Auto Electric ignition Using Spark Plug.docx

7/26/2019 Auto Electric ignition Using Spark Plug.docx

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ABSTRACT

Spark ignition engines utilize ignition systems that can developup to about 30 kV for breakdown of the spark plug gap and

typically deliver current levels in the range of 30 to 100 mA.

easurement and analysis of these systems show that the

energy transfer e!ciency is very low" typically in the order of

one percent #1$% or less. &his operating level is ade'uate for

older and most modern engines" but will not meet the needs of

future lean burn and some alternate fuel engines that re'uire

higher energy discharges to e(ectively ignite the air)fuelmi*tures. &o meet the re'uirements for increased ignition

power and energy" ignition systems will have to be designed to

operate at higher transfer e!ciencies. &here are two basic

approaches to increasing the electrical e!ciency of ignition

systems. &he +rst is to utilize peaking capacitors across the

spark plug. &he second is to design and utilize a more e!cient

discharge circuit in combination with a low resistance spark

coil. A third alternative would be to utilize a combination ofboth. ,y the +rst method" transfer e!ciency can be increased

to nearly +fty percent #-0$%. ,y the third" transfer e!ciency

can be seventy+ve percent #/-$% or more. &his paper

summarizes the results of high power ignition e*periments and

related analyses" for socalled breakdown ignition conditions.

&he paper includes descriptions of both conventional system

upgrades and a new higher energy system that features

multiple drivers and an energy recovery circuit. t does notinclude analyses or e*periments for arc or glow discharge

conditions.


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Introduction

Learning Objective:

dentify charging" starting" ignition" and accessorycircuit

components" their functions" and maintenance procedures.

dentify the basic types of automotive wiring" types of

terminals" and wiring diagrams. &he electrical systems on

e'uipment used by the 2avy are designed to perform a variety

of functions. &he automotive electrical system contains +ve

electrical circuits.

&hese circuits are as follows #+g. 1%4

1. 5harging circuit". Starting circuit"3. gnition circuit6. 7ighting circuit-. Accessory circuit

8lectrical power and control signals must be delivered to

electrical devices reliably and safely so electrical system

functions are not impaired or converted to hazards. &his goal is

accomplished through careful circuit design" prudent

component selection" and practical e'uipment location. ,y

carefully studying this chapter and the preceding chapter" you

will understand how these circuits work and the ad9ustments

and repairs re'uired to maintain the electrical systems in peak

condition.


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Learning Objective: dentify chargingcircuit components"

their functions" and maintenance procedures. &he charging

system performs several functions" which are as follows4 t

recharges the battery after engine cranking or after the use of

electrical accessories with the engine turned o(. t supplies all


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the electricity for the vehicle when the engine is running. t

must change output to meet di(erent electrical loads.

t provides a voltage output that is slightly higher than battery

voltage. A typical charging circuit consists of the following4

,A&&8:; provides current to energize or e*cite the alternator

and assists in stabilizing initial alternator output. A7&8:2A&


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BATTERY CONSTRUCTION&he leadacid celltype storage battery is built to withstand

severe vibration" cold weather" engine heat" corrosive

chemicals" high current discharge" and prolonged periods

without use. &o test and service batteries properly" you must

understand battery construction. &he construction of a basic

leadacid celltype battery is as follows4

,attery element

,attery case" cover" and caps

8lectrolyte

,attery terminals

BATTERY ELEMENT.

&he battery element is made up of negative plates" positive

plates" separators" and straps #+g. 3%. &he element +ts into a


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cell compartment in the battery case. ost automotive

batteries have si* elements.

8ach cell compartment contains two kinds of chemically activelead plates" known as positive and negative plates. &he battery

plates are made of =:? #sti( mesh framework% coated with

porous lead. &hese plates are insulated from each other by

suitable separators and are submerged in a sulfuric acid

solution #electrolyte%.

5harged negative plates contain spongy #porous% lead #@b%which is gray in color. 5harged positive plates contain lead

pero*ide #@b


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#microporous rubber" +brous glass" or plasticimpregnated

material%" called separators" are inserted between the plates.

&hese separators are thin and porous so the electrolyte will ow

easily between the plates. &he side of the separator that is

placed against the positive plate is grooved so the gas that

forms during charging will rise to the surface more readily.

&hese grooves also provide room for any material that akes

from the plates to drop to the sediment space below.

BATTERY CASE COYER AN! CA"S#

&he battery case is made of hard rubber or a high 'uality

plastic. &he case must

withstand e*treme vibration" temperature change" and the

corrosive action of the

electrolyte. &he dividers in the case form individual containers

for each element. A container with its element is one cell.

Sti( ridges or ribs are moulded in the bottom of the case to

form a support for the plates and a sediment recess for the

akes of active material that drop o( the plates during the life

of the battery. &he sediment is thus kept clear of the plates so it

will not cause a short circuit across them.

&he battery cover is made of the same material as the

container and is bonded to and seals the container. &he cover

provides openings for the two battery posts and a cap for each

cell.

,attery caps either screw or snap into the openings in the

battery cover. &he battery caps #vent plugs% allow gas to

escape and prevent the electrolyte from splashing outside the


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battery. &hey also serve as spark arresters #keep sparks or

ames from igniting the gases inside the battery%. &he battery

is +lled through the vent plug openings. aintenancefree

batteries have a large cover that is not removed during normal

service.

CAUTION

Bydrogen gas can collect at the top of a battery. f this gas is

e*posed to a ame or spark" it can e*plode.

BATTERY TERMINALS#$ ,attery terminals provide a means of

connecting the battery plates to the electrical system of the

vehicle. 8ither two round post or two side terminals can be

used.

,attery terminals are round metal posts e*tending through the

top of the battery cover. &hey serve as connections for battery

cable ends. @ositive post will be larger than the negative post. t

may be marked with red paint and a positive #C% symbol.

2egative post is smaller" may be marked with black or green

paint" and has a negative #% symbol on or near it.

Side terminals are electrical connections located on the side of

the battery. &hey have internal threads that accept a special

bolt on the battery cable end. Side terminal polarity is identi+ed

by positive and negative symbols marked on the case.

ELECTROLYTE# &he electrolyte solution in a fully charged

battery is a solution of concentrated sulphuric acid in water.

&his solution is about D0 percent water and about 60 percent

sulphuric acid. &he electrolyte in the leadacid storage battery

has a speci+c gravity of 1.E" which means that it is 1.E times


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as heavy as water. &he amount of sulphuric acid in the

electrolyte changes with the amount of electrical chargeF also

the speci+c gravity of the electrolyte changes with the amount

of electrical charge. A fully charged battery will have a speci+c

gravity of 1.E at E0G H. &he +gure will go higher with a

temperature decrease and lower with a temperature increase.

electrolyte changes with the amount of electrical chargeF also

the speci+c gravity of the electrolyte changes with the amount

of electrical charge. A fully charged battery will have a speci+c

gravity of 1.E at E0G H. &he +gure will go higher with a

temperature decrease and lower with a temperature increase.

As a storage battery discharges" the sulphuric acid is depleted

and the electrolyte is gradually converted into water. &his

action provides a guide in determining the state of discharge of

the leadacid cell. &he electrolyte that is placed in a leadacid

battery has a speci+c gravity of 1.E0.

&he speci+c gravity of an electrolyte is actually the measure of

its density. &he

electrolyte becomes less dense as its temperature rises" and a

low temperature means a high speci+c gravity. &he hydrometer

that you use is marked to read speci+c gravity at E0G H only.

>nder normal conditions" the temperature of your electrolyte

will not vary much from this mark. Bowever" large changes in

temperature re'uire a correction in your reading.


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Hor 8V8:; 10degree change in temperature A,,&:A5& 0.006 from your speci+c gravity reading. Suppose

you have 9ust taken the gravity reading of a cell. &he

hydrometer reads 1.E0. A thermometer in the cell indicates an

electrolyte temperature of D0G H. &hat is a normal di(erence of

0 degrees from the normal of E0G H. &o get the true gravity

reading" you must subtract 0.00E from 1.E0. &hus the speci+c

gravity of the cell is actually 1./. A hydrometer conversion

chart similar to the one shown in +gure 6 is usually found on

the hydrometer. Hrom it" you can obtain the speci+c gravity

correction for temperature changes above or below E0G H.

Higure 6. Bydrometer conversion chart.


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BATTERY CA"ACITY

&he capacity of a battery is measured in amperehours. &he

amperehour capacity is e'ual to the product of the current in

amperes and the time in hours during which the battery is

supplying current. &he amperehour capacity varies inversely

with the discharge current. &he size of a cell is determined

generally by its amperehour capacity. &he capacity of a cell

depends upon many factors" the most important of which are

as follows4

1. &he area of the plates in contact with the electrolyte

. &he 'uantity and speci+c gravity of the electrolyte

3. &he type of separators

6. &he general condition of the battery #degree of sulfating"

plates buckled" separators warped" sediment in bottom of cells"

etc.%

-. &he +nal limiting voltage

Batter% Rating&

,attery ratings were developed by the Society of Automotive

8ngineers #SA8% and the ,attery 5ouncil nternational #,5%.

&hey are set according to national test standards for battery

performance. &hey let the mechanic compare the cranking

power of one battery to another. &he two methods of rating

leadacid storage batteries are the cold cranking rating and the

reserve capacity rating.

COL!$CRAN'ING RATING#$ &he coldcranking rating

determines how much current in amperes the battery can

deliver for thirty seconds at 0G H while maintaining terminal


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&here are several methods for charging batteriesF only direct

current is used with each method. f only alternating current is

available" a recti+er or motor generator must be used to

convert to direct current. &he two principal methods of charging

are #1% constant current and #% constant voltage #constant

potential%. 5onstant current charging is be used on a single

battery or a number of batteries in series. 5onstant voltage

charging is used with batteries connected in parallel. #A parallel

circuit has more than one path between the two source

terminalsF a series circuit is a onepath circuit%. ;ou should know

both methods" although the latter is most often used.

CONSTANT CURRENT C)ARGING#$

Iith the constant current method" the battery is connected to a

charging device that supplies a steady ow of current. &he

charging device has a recti+er #a gas+lled bulb or a series of

chemical disks%F thus" the alternating current is changed into

direct current. A rheostat #resistor for regulating current% of

some kind is usually built into the charger so that you can

ad9ust the amount of current ow to the battery.


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remains constant for hours" you can assume that the battery

will take no more charge.

&he primary disadvantage of constant current charging is that

&B8 5BA:=2= 5>::82& :8A2S A& A S&8A?; VA7>8 >278SS

; 5BA2=8 &. A battery charged with too high current rate

would overheat and damage the plates" making the battery

useless. ?o 2


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t is easy to connect the battery to the charger" turn the charging

current on" and" after a normal charging period" turn the charging

current o( and remove the battery. 5ertain precautions however are

necessary both ,8H:2= the charging period. &hese

practices are as follows4 1. 5lean and inspect the battery thoroughly

before placing it on charge. >se a solution of baking soda and water

for cleaningF and inspect for cracks or breaks in the container.

"LACING NE* BATTERIES IN SER(ICE

2ew batteries may come to you full of electrolyte and fully

charged. n this case" that is necessary is to install the batteries

properly in the piece of e'uipment. ost batteries shipped to

25H units are received charged and dry.

5harged and dry batteries will retain their state of full charge

inde+nitely so long as moisture is not allowed to enter the cells.

&herefore" batteries should be stored in a dry place. oisture

and air entering the cells will allow the negative plates to

o*idize. &he o*idation causes the battery to lose its charge. &o

activate a dry battery" remove the restrictors from the vents

and remove the vent caps. &hen +ll all the cells to the proper

level with electrolyte. &he best results are obtained when the

temperature of the battery and electrolyte is within the range

of D0G H to E0G H.

Some gassing will occur while you are +lling the battery due to

the release of carbon dio*ide that is a product of the drying

process of the hydrogen sul+de produced by the presence of

free sulphur. &herefore" the +lling operations should be in a

wellventilated area. &hese gases and odours are normal and

are no cause for alarm.


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Appro*imately - minutes after adding electrolyte" the battery

should be checked for voltage and electrolyte strength. ore

than D volts or more than 1 volts" depending upon the rated

voltage of the battery" indicates the battery is ready for service.

Hrom - to D volts or from 10 to 1 volts indicate o*idized

negative plates" and the battery should be charged before use.

7ess than - or less than 10 volts" depending upon the rated

voltage" indicates a bad battery" which should not be placed in

service.

f" before placing the battery in service" the speci+c gravity"

when corrected to E0G H" is more than .030 points lower than it

was at the time of initial +lling or if one or more cells gas

violently after adding the electrolyte" the battery should be fully

charged before use. f the electrolyte reading fails to rise during

charging" discard the battery. f" before placing the battery in

service" the speci+c gravity" when corrected to E0G H" is more

than .030 points lower than it was at the time of initial +lling or

if one or more cells gas violently after adding the electrolyte"

the battery should be fully charged before use. f the electrolyte

reading fails to rise during charging" discard the battery.

ost shops receive readymi*ed electrolyte. Some units may

still get concentrated sulphuric acid that must be mi*ed with

distilled water to get the proper speci+c gravity for electrolyte.

L2= 8785&:


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may re'uire hours of safe dilution.

Higure - shows you how much water and acid to mi* for

obtaining a certain speci+c gravity. Hor e*ample" mi*ing - parts

of water to parts of acid produces an electrolyte of 1.300"

when starting with 1.E3- speci+c gravity acid. f you use 1.600

speci+c gravity acid" parts water and - parts acid will give the

same results.

7et the mi*ed electrolyte cool down to room temperature

before adding it to the

battery cells. Bot electrolyte will eat up the cell plates rapidly.

&o be on the safe side" do not add the electrolyte if its

temperature is above K0G H. After +lling the battery cells" let the

electrolyte cool again because more heat is generated by its

contact with the battery plates. 2e*t" take hydrometer

readings. &he speci+c gravity of the electrolyte will correspond

'uite closely to the values on the mi*ing chart if the parts of

water and acid are mi*ed correctly.

BATTERY MAINTENANCE

f a battery is not properly maintained" its service life will be

drastically reduced. ,attery maintenance should be done

during every @ cycle. 5omplete battery maintenance includes

the following4

Visually checking the battery.

5hecking the electrolyte level in cells on batteries with caps.

Adding water if the electrolyte level is low.

5leaning o( corrosion around the battery and battery terminals.


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Higure -. 8lectrolyte mi*ing chart.

BATTERY TEST

As a mechanic you will be e*pected to test batteries for proper

operation and

condition. &hese tests are as follows4

,attery leakage test

,attery terminal test,attery voltage test

5ell voltage test

,attery drain test

,attery load test #battery capacity test%

Muick charge test

BATTERY LEA'AGE TEST#$ A battery leakage test will

determine if current is discharging across the top of the battery.

A dirty battery can discharge when not in use. &his condition

shortens battery life and causes starting problems.

&o perform a battery leakage test" set a voltmeter on a low

setting. &ouch the probes on the battery" as shown in +gure D.

f any current is registered on the voltmeter" the top of the

battery needs to be cleaned.


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BATTERY TERMINAL TEST#$&he battery terminal test 'uickly

checks for poor electrical connection between the terminals

and the battery cables. A voltmeter is used to measure voltage

drop across terminals and cables.

&o perform a battery terminal test #+g. /%" connect the

negative voltmeter lead to the battery cable end. &ouch the

positive lead to the battery terminal. Iith the ignition or

in9ection system disabled so that the engine will not start" crank

the engine while watching the voltmeter reading.

Higure D. ,attery leakage test. Higure /. ,attery

terminal test.

BATTERY (OLTAGE TEST#

&he battery voltage test is done by measuring total battery voltage

with an accurate voltmeter or a special battery tester #+g. E%. &his

test determines the general state of charge and battery condition

'uickly.

&he battery voltage test is used on maintenancefree batteries

because these batteries do not have caps that can be removed for

testing with a hydrometer. &o perform this test" connect thevoltmeter or battery tester across the battery terminals. &urn on the


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vehicle headlights or heater blower to provide a light load. 2ow read

the meter or tester. A wellcharged battery should have over 1

volts. f the meter reads appro*imately 11.- volts" the battery is not

charged ade'uately" or it may be defective.

CELL (OLTAGE TEST#

&he cell voltage test will let you know if the battery is discharged or

defective. 7ike a

hydrometer cell test" if the voltage reading on one or more cells is .

volts or more lower than the other cells" the battery must be

replaced. &o perform a cell voltage test #+g. K%" use a low voltage

reading voltmeter with special cadmium #acid resistant metal% tips.

nsert the tips into each cell" starting at one end of the battery and

work your way to the other. &est each cell carefully. f the cells are

low" but 'uall recharging usually will restore the battery. f cell

voltage readings vary more than . volts" the battery is ,A?.

Higure E. ,attery voltage test performed with a battery tester.


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Higure K. 5ell voltage test.

,A&&8:; ?:A2 &8S&. A battery drain test checks for abnormal

current draw

with the ignition o(. f a battery goes dead without being used" you

need to check for a current drain.

&o perform a battery drain test" set up an ammeter" as shown in

+gure 10. @ull the fuse if the vehicle has a dash clock. 5lose

all doors and trunk #if applicable%. &hen read the ammeter. f

everything is o(" there should be a zero reading. Any reading

indicates a problem. &o help pinpoint the problem" pull fuses

one at a time until there is a zero reading on the ammeter. &his

action isolates the circuit that has the problem.

BATTERY CA"ACITY TEST#$

A battery load test" also termed a battery capacity test" is the

best method to check battery condition. &he battery load test

measures the current output and performance of the battery

under full current load. t is one of the most common and

informative battery tests used today.


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,efore load testing a battery" you must calculate how much

current draw should be applied to the battery. f the ampere

hour rating of the battery is given" load the battery to three

times its amphour rating. Hor e*ample" if the battery is rated at

D0 amphours" test the battery at 1E0 amps #D0 * 3 N 1E0%. &he

ma9ority of the batteries are now rated in SA8 coldcranking

amps" instead of amphours. &o determine the load test for

these batteries" divide the coldcrank rating by two. Hor

e*ample" a battery with 600 cold cranking amps rating should

be loaded to 00 amps #600 O N 00%. 5onnect the battery

load tester" as shown in +gure 11. &urn the control knob until

the ammeter reads the correct load for your battery.

After checking the battery charge and +nding the amp load

value" you are ready to test battery output. ake sure that the

tester is connected properly. &urn the load control knob until the

ammeter reads the correct load for your battery. Bold the load

for 1- seconds. 2e*t" read the voltmeter while the load is

applied.


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+UIC' C)ARGE TEST#$

&he 'uick charge test" also known as 3minute charge test"

determines if the battery is sulphated. f the results of the

battery load test are poor" fast charge the battery. 5harge the

battery for 3 minutes at 30 to 60 amps. &est the voltage while

charging. f the voltage goes A,


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must be constructed according to the number of +eld poles because

current is generated when the coil #winding on the armature% moves

across each magnetic circuit. Higure 1. Sectional view of a dc

generator. &he current is collected from the armature coils by

brushes #usually made of carbon% that make rubbing contact with a

commentator. &he commutator consists of a series of insulated

copper segments mounted on one end of the armature" each

segment connecting to one or more armature coils. &he armature

coils are connected to the e*ternal circuits #battery" lights" or

ignition% through the commutator and brushes. 5urrent induced in

the armature coils thus is able to ow to the e*ternal circuits. &here

are two types of +eld circuits" determined by the point at which the

+eld circuit is grounded" which are as follows4

Higure 1. Sectional view of a dc generator


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IGNITION CIRCUIT

&he ignition circuit supplies high voltage surges #some as high

as -0"000 volts in electronic ignition circuits% to the spark plugs

in the engine cylinders. &hese surges produce electric sparks

across the spark plug gaps. &he heat from the spark ignites the

compressed airfuel mi*ture in the combustion chambers. Ihen

the engine is idling" the spark appears at the spark plug gap

9ust as the piston nears top dead center #&?5% on the

compression stroke. Ihen the engine is operating at higher

speeds" the spark is advanced. t is moved ahead and occurs

earlier in the compression stroke. &his design gives the

compressed mi*ture more time to bum and deliver its energy to

the pistons. &he functions of

an ignition circuit are as follows4

1. @rovide a method of turning the ignition circuit


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D. Vary spark timing with engine speed" load" and other

conditions.

"RIMARY AN! SECON!ARY CIRCUITS

&he ignition circuit is actually made of two separate circuits

which work together to cause the electric spark at the spark

plugs. &hese two circuits are the @:A:; and S85


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!"#!T!$# 0!%TR!B1T$R- distri+utesignition voltage to the spar2 plug.

'ontains either mechanical contact points or an electronic switching circuit.

%3AR4 3*1"- device that provides an air gap in the com+ustion cham+er for

an electric arc.

Ignition S.itc/

&he ignition switch #+g. 63% enables the operator to turn the

ignition on for starting and running the engine and to turn it o(

to stop the engine. ost automotive ignition switches

incorporate four positions" which are as follows4

O00

&he


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terminals #low voltage connections%" an iron core #long piece of

iron inside the windings%" and a high voltage terminal #coil wire

connection%. &he primary winding is the outer winding and is

made up of several hundred turns of heavy wire" wrapped

around or near the secondary winding. &he secondary winding

is the inner winding and is made up of several thousand turns

of heavy wire located inside or near the primary winding. &he

secondary windings are wound in the opposite direction of the

primary" and the ends are attached internally to the primary

windings and the high voltage terminal. ,oth windings are

wrapped around an iron core and are housed inside the coil

case. &o obtain the high current re'uired for ignition" battery

current ows through the ignition coil primary windings

producing a strong magnetic +eld. &he action of the iron core

strengthens the magnetic +eld.

)igure 6-77.- %ectional view of an ignition coil

&hen the current flowing through the coil is +ro2en (the primar, circuit is

opened/ the magnetic field collapses across the secondar, windings. As the

magnetic field collapses/ a high

electrical voltage is induced into the

secondar, circuit. %ince +oth the

primar, and secondar, windings of the

coil are stationar,/ some means otherthan movement of the windings must


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+e found to change the magnetic field surrounding the coils. !n practice/ a

switching device in the primar, circuit creates this effect. There are two

common methods to +rea2 current flow and fire the coil mechanical contact

points or an electronic switching device.

IGNITION !ISTRIBUTOR

An ignition distributor can be a contact point or pickup coil

type" as shown in +gure 6-. A contact point distributor is

commonly found in older vehicles" whereas the pickup coil type

distributor is used on many modern vehicles. &he ignition

distributor has several functions" which are as follows4

t actuates the


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Higure 6-. 5omparison of a #A% contact point distributor and a

#,% pickup coil

?istributor.

!ISTRIBUTOR CA"#$&he distributor cap is an insulating plastic

component that

covers the top of the distributor housing. ts centre terminal

transfers voltage from the coil wire to the rotor. &he distributor

cap also has outer terminals that send electric arcs to the spark


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plugs. etal terminals are molded into the plastic cap to

provide electrical connections.

!ISTRIBUTOR ROTOR#$&he distributor rotor transfers voltage

from the coil wire to the spark plug wires. &he rotor is mounted

on top of the distributor shaft. t is an electrical switch that

feeds voltage to each spark plug wire in turn.

A metal terminal on the rotor touches the distributor cap center

terminal. &he outer end of the rotor A7


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vehicles re'uire resistor type plugs. 2onresistor spark plug has

a solid metal rod forming the center electrode. &his type of

spark plugs is 2


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the plug. &hen high voltage surges would leak across the

carbon instead of producing a spark across the spark plug gap.

>sing a hotter plug will bum this carbon deposit away or

prevent it from forming. Spark plug reach is the distance

between the end of the spark plug threads and the seat or

sealing surface of the plug. @lug reach determines how far the

plug reaches through the cylinder head. f spark plug reach is

too long" the spark plug will protrude too far into the

combustion chamber and the piston at &?5 may strike the

electrode.

Bowever" if the reach is too short" the plug electrode may not

e*tend far enough into the cylinder head and combustion

e!ciency will be reduced. A spark plug must reach into the

combustion chamber far enough so that the spark gap will be

properly positioned in the combustion chamber without

interfering with the turbulence of the airfuel mi*ture or

reducing combustion action.


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)igure 6-78.- %ectional view of a (A non-resistor and (B resistor spar2 plug.

S"AR' "LUG *IRES

&he spark plug wires carry the high voltage electric current

from the distributor cap side terminals to the spark plugs. n

vehicles with distributorless ignition" the spark plug wires carry

coil voltage directly to the spark plugs. &he two types of spark

plug wires are as follows4

S


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ohms per foot. &his prevents highvoltage induced

popping or cracking of the radio speakers.

&


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5


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ELECTRONIC IGNITION SYSTEM&he basic di(erence between the contact point and the

electronic ignition system is in the primary circuit. &he primary

circuit in a contact point ignition system is open and closed by

contact points. n the electronic system" the primary circuit is

open and closed by the electronic control unit #85>%.

&he secondary circuits are practically the same for the twosystems. &he di(erence is that the distributor" ignition coil" and

wiring are altered to handle the high voltage produced by the

electronic ignition system.


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@5Q>@ 5 dwell time #number of degrees the circuit conducts

current to the ignition coil% is designed into the electronic circuit

of the 85> and is 2


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current passes through the primary windings of the ignition coil"

thereby developing a magnetic +eld. &hen" when the trigger

wheel and pickup coil turn " the magnetic +eld

inside the ignition coil collapses and +res a sparkplug.

)a33$E5ect Sen&or

Some electronic distributors have a magnetic sensor using the

Ball e(ect. Ihen a steel shutter moves between the two poles

of a magnet" it cuts o( the magnetism between the two poles.

&he Balle(ect distributor has a rotor with curved plates" called

shutters. &hese shutters are curved so they can pass through

the air gap between the two poles of the magnetic sensor" as

the rotor turns. 7ike the trigger wheel" there are the same

number of shutters as there are engine cylinders.

8ach time a shutter mo ves through the air gap between the

two poles of the magnetic sensor" it cuts o( the magnetic +eld

between the poles. &his action provides a signal to the 85>.

Ihen a shutter is not in the way" the magnetic sensor is

producing voltage. &his voltage is signaling the 85> to allow

current to ow through the ignition coils primary winding.

Bowever" when the shutter moves to cut o( the magnetic +eld"

the signal voltage drops to zero. &he 85> then cuts o( the

current to the ignition coils primary winding. &he magnetic +eld

collapses" causing the coil secondary winding to produce a high

voltage surge. &his high voltage surge is sent by the rotor to

the proper spark plug.

IGNITION TIMING !E(ICES


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gnition timing refers to how early or late the spark plugs +re in

relation to the position of the engine pistons. gnition timing

must vary with engine speed" load" and temperature.

&iming advance happens when the spark plugs +re sooner than

the compression strokes of the engine. &he timing is set several

degrees before top dead center #&?5%.

ore time advance is re'uired at higher speeds to give

combustion enough time to develop pressure on the power

stroke.&iming retard happens when the spark plugs +re later on

the compression strokes. &his is the opposite of timing

advance. Spark retard is re'uired at lower speeds and under

high load conditions. &iming retard prevents the fuel from

burning too much on the compression stroke" which would

cause spark knock or ping.

&he basic methods to control ignition system timing are as

follows4

582&:H>=A7 A?VA258 #controlled by engine speed%

VA5>> A?VA258 #controlled by intake manifold vacuum and

engine load%

5&8:R8? A?VA258 #controlled by various sensors

speed" temperature"

intake" vacuum" throttle position" etc.%

Centri6uga3 Advance

5entrifugal advance makes the ignition coil and spark plugs +re

sooner as engine speed increases" using springloaded weights"

centrifugal force" and lever action to rotate the distributor cam


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or trigger wheel. Spark timing is advanced by rotating the

distributor cam or trigger wheel against distributor shaft

rotation. &his action helps correct ignition timing for ma*imum

engine power. ,asically the centrifugal advance consists of two

advance weights" two springs" and a advance lever.

?uring periods of low engine speed" the springs hold the

advance weights inward towards the distributor cam or trigger

wheel. At this time there is not enough centrifugal force to push

the weights outward. &iming stays at its normal initial setting.

As speed increases" centrifugal force on the weights moves

them outwards against spring tension. &his movement causes

the distributor cam or trigger wheel to move ahead. Iith this

design" the higher the engine speed" the faster the distributor

shaft turns" the farther out the advance weights move" and the

farther ahead the cam or trigger wheel is moved forward or

advanced. At a preset engine speed" the lever strikes a stop

and centrifugal advance reaches ma*imum.

&he action of the centrifugal advance causes the contact points

to open sooner" or the trigger wheel and pickup coil turn o( the

85> sooner. &his causes the ignition coil to +re with the engine

pistons not as far up in the cylinders.

(acuu4 Advance

&he vacuum advance provides additional spark advance when

engine load is low at part throttle position. t is a method of

matching ignition timing with engine load. &he vacuum

advance increases H>87 85


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of a vacuum diaphragm" link" movable distributor plate" and a

vacuum supply hose.

At idle" the vacuum port from the carburetor or throttle body to

the distributor advance is covered" thereby 2< vacuum is

applied to the vacuum diaphragm" and spark timing is 2


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82=28 5


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open throttle and other sensor outputs say the same. &he

computer receives and calculates the data" then" if re'uired"

retards ignition timing to prevent spark knock or ping.

IGNITION SYSTEM MAINTENANCE

gnition troubles can result from a myriad of problems" from

faulty components to loose or damaged wiring. >nless the

vehicle stops on the 9ob" the operator will report trouble

indications" and the e'uipment is turned into the shop for

repairs.

>nless the trouble is known" a systematic procedure should be

followed to locate the cause. :emember" that electric current

will follow the path of least resistance. &race ignition wiring

while checking for grounds" shorts" and open circuits. ,are

wires" loose connections" and corrosion are found through

visual inspection.

After checking the system" you must evaluate the symptoms

and narrow down the possible causes. >se your knowledge of

system operation" a service manual troubleshooting chart"

basic testing methods" and common sense to locate the

trouble. any shops have specialized e'uipment that provide

the mechanic a 'uick and easy means of diagnosing ignition

system malfunctions.

S1ar2 "3ug& and S1ar2 "3ug *ire&

,ad spark plugs cause a wide range of problems mis+ring" lack

of power" poor fuel economy" and hard starting. After prolonged

use" the spark pl ug tip can become coated with ash" oil" and

other residue. &he spark plug electrodes can also bum and


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widen the gap. &his makes it more di!cult for the ignition

system to produce an electric arc between the electrodes.

&o read spark plugs closely" inspect and analyze the condition

of each spark plug tip and insulator. &his will give you

information on the condition of the engine" the fuel system" and

the ignition system. &he conditions commonly encountered with

spark plugs areas follows4

2


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)igure 6-79.-

#ormal operation.

)igure 6-7.- 'ar+on fouled.

)igure 6-7;.- $il fouled.

ASB H78? #+g. -0% appears as

red" brown" yellow" or white

coloured deposits which

accumulate on the insulator"

resulting from poor fuel 'uality or

oil entering the cylinder. ost ash

deposits have no adverse e(ect on


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the operation of the spark plug as long as they remain in a

powdery state. Bowever" under certain conditions these

deposits melt and form a shiny glaze on the insulator which"

when hot" acts as a good electrical conductor. &his allows

current to follow the deposit instead of 9umping the gap" thus

shorting out the spark plug. Spark plugs" having a powdery

condition" may be cleaned" regapped" and replaced. &hose

having a glazed deposit are to be replaced.

@:8=2&


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)igure 6-


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reaching the spark plugs. &o test the wires for proper operation"

you can perform the following4

A SPARK PLUG WIRE RESISTANCE TEST

Iill check the spark plug conductor or coil wire conductor. &o

perform a wire resistance test" connect an ohmmeter across

each end of the wire. &he meter will read internal wire

resistance in ohms. &ypically resistance should 2


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timing" and distributes high voltage to the spark plugs. f any

part of the distributor is faulty" engine performance su(ers.

!ISTRIBUTOR CA" AN! ROTOR#$ Ihen problems point to

possible distributor

cap or rotor troubles" remove and inspect them. &he distributor

cap should be carefully checked to see that sparks have not

been arcing from point to point. ,oth interior and e*terior must

be clean. &he +ring points should not be eroded" and the

interior of the towers must be clean.

&he rotor tip" from which the hightension spark 9umps to each

distributor cap

&erminal" should not be worn. t also should be checked for

e*cessive burning" carbon trace" looseness" or other damage.

Any wear or irregularity will result in e*cessive resistance to the

hightension spark. ake sure that the rotor +ts snugly on the

distributor shaft.

CONTACT "OINT !ISTRIBUTOR SER(ICE#$ n a contact point

distributor" there are two areas of concern the contact points

and the condenser. ,ad contact points cause a variety of

engine performance problems. &hese problems include high

speed missing" nostart problem" and many other ignition

troubles. Visually inspect the surfaces of the contact points to

determine their condition. @oints with burned and pitted

contacts or with a worn rubbing block must be replaced.

Bowever" if the points look good" point resistance should be

measured. &urn the engine over until the points are closed and

then use an ohmmeter to connect the meter to the primary


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point lead and to ground. f resistance reading is too high" the

points are burned and must be replaced.

A faulty condenser may leak #allow some dc current to ow to

ground%" be shorted #direct electrical connection to ground%" or

be opened #broken lead wire to the condenser foils%. f the

condenser is leaking or open" it will cause point arcing and

burning. f the condenser is shorted" primary current will ow to

ground and the engine will 2


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electrical impulses to the 85>. f the distributor fails to produce

these electrical impulses properly" the ignition system can 'uit

functioning.

A faulty pickup coil will produce a wide range of engine

troubles" such as stalling" oss


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Iith one tooth of the trigger wheel pointing at the pickup coil"

slide the correct thickness nonmagnetic feeler gauge between

the trigger wheel and the pickup coil. ove the pickup coil in or

out until the correct air gap is set. &ighten the pickup coil

screws and doublecheck the air gap setting.

Ignition Ti4ing

&he ignition system must be timed so the sparks 9ump across

the spark plug gaps at e*actly the right time. Ad9usting the

distributor on the engine so that the spark occur sat this correct

time is called setting the ignition timing. &he ignition timing is

normally set at idle or a speed speci+ed by the engine

manufacturer. ,efore measuring engine timing" disconnect and

plug the vacuum advance hose going to the distributor. &his

action prevents the vacuum advance from functioning and

upsetting the readings. Ad9ustment is made by loosening the

distributor holddown screw and turning the distributor in its

mounting.

&urning the distributor housing against the distributor shaft

rotation A?VA258S &B8 &2=. &urning the distributor housing

with shaft rotation :8&A:?S &B8&2=. :efer to +gure -3.

Ihen the ignition timing is &


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ames blowing out of the open e*haust valve can overheat the

engine and crack the e*haust manifolds.

)igure 6-,8:


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r in

harmonic balance of the engine" or they may be on the engine

ywheel.

Iith the engine running" aim the ashing timing light at the

timing mark and

reference pointer. &he ashing timing light will make the mark

appear to stand still. f the timing mark and the pointer do not

line up" turn the distributor in its mounting until the timing

mark and pointer are aligned. &ighten the distributor holddown

screw.

LIG)TING CIRCUIT

Learning Objective: dentify lightingcircuit components" their

functions" and

maintenance procedures.

&he lighting circuit #+g. -6% includes the battery" vehicle

frame" all the lights" and various switches that control their use.


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&he lighting circuit is known as a singlewire system since it

uses the vehicle frame for the return.

&he complete lighting circuit of a vehicle can be broken down

into individual circuits" each having one or more lights and

switches. n each separate circuit" the lights are connected in

parallel" and the controlling switch is in series between the

group of lights and the battery. &he marker lights" for e*ample"

are connected in parallel and are controlled by a single switch.

n some installations" one switch controls the connections to the

battery" while a selector switch determines which of two circuits

is energized. &he headlights" with their high and low beams" are

an e*ample of this type of circuit.

n some instances" such as the courtesy lights" several switches

may be connected in parallel so that any switch may be used to

turn on the light.

Ihen a wiring diagram is being studied" all light circuits can be

traced from the

battery through the ammeter to the switch #or switches% to the

individual light.

LAM"S

Small gas+lled incandescent lamps with tungsten +laments are

used on automotive

and construction e'uipment #+g. --%. &he +laments supply

the light when su!cient

current is owing through them. &hey are designed to operate

on a low voltage current

of 1 or 6 volts" depending upon the voltage of the the vehicle

will be of the singleor


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doublecontact small onehalfcandlepower bulbs to large -0

candlepower bulbs. &he

greater the candlepower of the lamp" the more current it

re'uires when lighted. 7amps are identi+ed by a number on the

base. Ihen you replace a lamp in a vehicle" be sure the new

lamp is of the proper rating. &he lamps within 7amps are rated

as to size by the candlepower #luminous intensity% they

produce. &hey range from types with nibs to +t bayonet

sockets" as shown in lamp is also whiter than a conventional

lamp" which increases lighting ability.


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Higure -D.# A% Singlecontact bulbF #,% ?oublecontact bulb.

)igure 6-


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)igure 6-


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without operating the mechanical switch to get blackout marker

lights #including blackout taillights and stoplights% and blackout

driving lights. ,ut for stoplights for daylight driving or

headlights for ordinary night driving" you must +rst lift the

mechanical switch lever and then turn the main switch to the

right. &he au*iliary switch gives panel lights when the main

switch is in any of its


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)igure 6-8=.- )loor-mounted dimmer switch.

)igure 6-86.- %teering column mounted dimmer switch.

n one position" the high beams are turned on" and" in the other

position" the dimmer changes them to low beam.Ai4ing )ead3ig/t&

&he headlights can be aimed using a mechanical aimer or a

wall screen. 8ither method assures that the headlight beams

point in the direction speci+ed by the vehicle manufacturer.

Beadlights that are aime d too high can blind oncoming

vehicles. Beadlights that are aimed too low or to one side will

reduce the operatorPs visibility.&o ensure that the headlights

are properly aimed" you should have a half a tank of fuel" the

correct tire pressure" and only the spare tire and 9ack in the

vehicle. Some manufacturers recommend that someone sit in

the operator and passenger seats while aiming the lights.

B8A?7=B& A8:S are a device for pointing the vehicle

headlights in a speci+ed position. &hey may be permanently


63/73

installed on a track or may be portable. Some re'uire a level

oor" and others have internal levelling mechanisms to allow

for uneven shop oors. &o use the aimer" follow the instructions

for the speci+c type of e'uipment.

&he B8A?7=B& A2= S5:882 is a series of measured lines

marked on a shop wall or on a framed easel for aiming the

headlights of a vehicle. &he screen should beno less than 10

feet wide and 6 inches high. Ihen it is mounted on an easel

with casters" the screen should be no more than 1 inches from

the oor. &o comply with regulations of most localities" you

should place the screen - feet ahead of the vehicle.

)igure 6-8.- Accepted +eam pattern for aiming passenger vehicle headlights


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Higure D6. Accepted beam pattern for a fourheadlight

&%&te4#

BLAC'OUT LIG)TS

,lackout lighting is a re'uirement for certain combat

operations. &he purposes of blackout lighting are as follows4

&o provide the vehicle operator with su!cient light to operate

the vehicle in total darkness

to provide the vehicle operator with su!cient light to operate

vehicle in total darkness

&o provide minimum lighting to show vehicle position to a

leading or trailing vehicle when illumination must be restricted

to a level not visible to a distant enemy

&he three types of blackout lighting are as follows4

&he ,7A5Q& ?:V2= 7=B& #+g. D-% is designed to provide

a white light of

- to -0 candlepower at a distance of 10 feet directly in front of

the light. &he light is shielded so that the top of the low beam is

directed not less than degrees below the horizon. &he beam

distribution on a level road at 100 feet from the light is 30 feet

wide.


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)igure 6-8


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)igure 6-88.- Blac2out stop> taillight and mar2er light.

)igure 6-89.- ?ilitar, composite light.

,lackout lighting control switches are designed to prevent the

service lighting from being turned on accidentally. &heir

operation is described in the Beadlight Switch section of this

&:AA2.

TURN$SIGNAL SYSTEMS

Vehicles that operate on any public road must be e'uipped with

turn signals. &hese signals indicate a left or right turn by

providing a ashing light signal at the rear and front of the

vehicle.

&he turnsignal switch is located on the steering column #+g.

DE%. t is designed to shut o( automatically after the turn is

completed by the action of the cancelling cam.

Higure DE. &ypical turnsignal switch.

A wiring diagram for a typical turnsignal system is shown in

+gure DK. A common design for a turnsignal system is to use


67/73

the same rear light for both the stop and turn signals. &his

somewhat complicates the design of the switch in that the

stoplight circuit must pass through the turnsignal switch. Ihen

the turnsignal switch is turned o(" it must pass stoplight

current to the rear lights. As a left or right turn signal is

selected" the stoplight circuit is open and the turnsignal circuit

is closed to the respective rear light.

&he turn signal asher unit #+g. /0% creates the ashing of

the turn signal lights. t consists basically of a bimetallic #two

dissimilar metals bonded together% strip wrapped in a wire coil.

&he bimetallic strip serves as one of the contact points.

Ihen the turn signals are actuated" current ows into the

asher +rst through the heating coil to the bimetallic strip"

then through the contact points" then out of the asher" where

the circuit is completed through the turnsignal light. &his

se'uence of events will repeat a few times a second" causing a

steady ashing of the turn signals.

BAC'U" LIG)T SYSTEM

&he backup light system provides visibility to the rear of the

vehicle at night and a warning to the e'uipped vehicles is

combined with the neutral safety switch pedestrians" whenever

the vehicle is shifted into reverse. &he backup light system has

a fuse" gearshiftor transmissionmounted switch" two backup

lights" and wiring to connect these components.


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)igure 6-8;.- T,pical turn-signal wiring diagram.

)igure 6-9.- Turn signal flasher.

&he backup light switch closes the light circuit when the

transmission is shifted into reverse. &he most common backup

light switch con+gurations are as follows4

&he backup light switch mounted on the transmission and

operated by the shift lever.


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&he backup light switch mounted on the steering column and

operated by the gearshift linkage.

&he transmissionor gearshiftmounted backup light switch on

many automatic

&ransmission.

TEM"ERATURE GAUGE

&he temperature gauge is a very important indicator in

construction and automotive e'uipment. &he most common

uses are to indicate engine coolant" transmission" di(erential

oil" and hydraulic system temperature. ?epending on the type

of e'uipment" the gauge may be mechanical" electric" or a

warning light.

&he 8785&:5 =A>=8 may be the thermostatic or magnetic

type" as described

previously. &he sending unit #+g. E3% that is used varies"

depending upon

application.

1. &he sending unit that is used with the thermostatic gauge

consists of two bimetallic strips" each having a contact

point.


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indicator light previously discussed.

)igure 6-6.- T,pes of sending units for pressure gauges

)igure 6-.- T,pes of temperature gauge sending units.

*IN!S)IEL! *I"ERS

&he windshield wiper system is one of the most importantsafety factors on any piece of e'uipment. A typical electricwindshield wiper system consists of a switch" motor assembly"wiper linkage and arms" and wiper blades. &he description ofthe components is as follows4

&he I2?SB87? I@8: SI&5B is a multi position switch"

which may contain a rheostat. 8ach switch position provides for

di(erent wiping speeds. &he rheostat" if provided" operates the

delay mode for a slow wiping action. &his permits the operator

to select a delayed wipe from every 3 to 0 seconds.


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A relay is fre'uently used to complete the circuit between the

battery voltage and the wiper motor.

&he I@8:


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)igure 6-;.- &iring diagram s,m+ols.

Conclusion

ence !or t"is pro#ect $e stu%ie% an% un%erstoo% a&out t"e

Electrical $or' %one in automo&ile section(

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Auto Electric ignition Using Spark Plug.docx