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Electrical SystemPreventive Maintence and
Diagnostic Procedures
Training Manual
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TABLE OF CONTENTS
SECTION 1: INTRODUCTION
1.1 Leece-Neville’s Training Manual forPreventive Maintenance and DiagnosticProcedures on Heavy-Duty Vehicles...........3
1.2 The Heavy-Duty Vehicle’sElectrical System..........................................3
1.3 The Importance of Using Proper PreventiveMaintenance Procedures..............................4
1.4 The Importance of Using Proper DiagnosticProcedures....................................................4
1.5 The Importance of Selecting the ProperElectrical Components.................................4
1.6 The Importance of Following SafetyPrecautions...................................................5
SECTION 2: THE BATTERY SYSTEM
2.1 An Overview of the Battery System............62.2 The Primary Causes of Battery System
Malfunction...............................................6-72.3 Preventive Maintenance Procedures............72.4 Diagnostic / Troubleshooting
Procedures.................................................7-92.5 Battery Charging..........................................92.6 Battery Replacement....................................9
SECTION 3: THE CHARGING SYSTEM
3.1 An Overview of the Charging System.......103.2 The Primary Causes of Charging System
Malfunction................................................103.3 Preventive Maintenance Procedures.....10-113.4 Diagnostic / Troubleshooting
Procedures.............................................11-123.5 Alternator Replacement..............................12
SECTION 4: THE STARTING SYSTEM
4.1 An Overview of the Starting System..............134.2 The Primary Causes of Starting System
Malfunction.....................................................134.3 Preventive Maintenance Procedures...............144.4 Diagnostic/Troubleshooting
Procedures.................................................14-164.5 Starter Replacement........................................16
5.1 The Benefits of Using Proper PreventiveMaintenance and Diagnostic Procedures........17
5.2 The Benefits of Selecting Proper ElectricalComponents.....................................................17
Appendix A Alternator Sizing Worksheet............18Appendix B Charging System Trouble Shooting
Flowchart..........................................19Appendix C Alternator Test Procedure
Flowchart..........................................20
SECTION 5: CONCLUSION
APPENDIX
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Leece-Neville’s Training Manual forPreventive Maintenance and Diagnos-tic Procedures on Heavy-Duty Vehicles
1.1
SECTION 1: INTRODUCTION
The objective of this training manual is to provide thecustomer with a step by step, easy to understand outlineof the procedures for maintaining and diagnosing aheavy-duty vehicle’s electrical system.
As a service technician, you should consider yourself asthe “doctor” who cares for your company’s heavy-dutyvehicles. It’s your responsibility to make sure thevehicles are well-maintained. And it’s your job toaccurately diagnose and repair equipment problems ifthey occur.
Unfortunately, problems with the vehicle’s electricalsystem are often misdiagnosed. What happens as aresult? Well, most industry studies indicate thatapproximately 55% of alternators and starters returnedunder warranty to manufacturers, and noted as “defec-tive”, are later discovered to be in fine working order.
Now it’s certainly true that electrical components canbecome damaged due to excessive heat and vibration,voltage spikes, careless handling and misapplication.Components can also become damaged by excessiveheat, whenever they are forced to operate at continu-ously high levels of electrical output. (For instance, thelatter addition of even a few accessories - such asmobile telephones, CB radios, portable CD players,coolers, microwaves, satellite tracking, bunk heaters,inverters, etc. - can overburden the amperage capacity ofthe originally installed alternator.)
Generally speaking, however, electrical components -such as alternators and starters - are designed to performtrouble- free for many thousands of miles.
So with knowledge and training, you’ll be able toproperly maintain your company’s vehicles. And ifproblems occur in the electrical system, you’ll be able toaccurately diagnose and correct them, instead ofimmediately assuming that an electrical componentitself is faulty.
That indeed is the goal of this training manual.
The Heavy-Duty Vehicle’s Electrical System1.2
If a technician does not have a clear understanding ofhow a vehicle’s electrical system works, it’s nearlyimpossible to accurately diagnose a problem.
A vehicle’s electrical system is comprised of threeelements: the battery system, the charging system, andthe starting system. All three systems work together asa team.
Figure 1: Vehicle electrical system
As with any team, each member has a specific andimportant job to perform. When diagnosing an electricalproblem, it’s necessary to consider each team member aspotentially contributing to the problem.
That’s why we’ve organized this training manual to coverthe battery system first, followed by the charging systemand finally the starting system.
You’ll find that each of these three sections starts with anoverview of how the system works, then moves on tocover various preventive maintenance and diagnostic (i.e.troubleshooting) procedures.
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The Importance of Using Proper PreventiveMaintenance Procedures
1.3
Throughout this manual, we’ll underscore the importanceof preventive maintenance, and show you the steps tobecome very proficient at it. Equally important, we’llshow you how to perform preventive maintenance safely.
The advantages of performing preventive maintenancecan be summarized in two ways. First, it enhances thelifespan of electrical components; and second, it improvesthe likelihood of trouble-free operation, thereby minimiz-ing vehicle downtime.
The Importance of Using Proper DiagnosticProcedures
1.4
There’s absolutely no question that diagnosing a problemin a vehicle’s electrical system can be tedious and timeconsuming. However, spending the upfront time requiredis much more efficient than having the vehicle’s drivercome back to you with an uncorrected problem. Simplyput, it’s important to take enough time to properlydiagnose and correct the real problem.
To accurately diagnose an electrical problem, you need toequip yourself with two things: the proper tools and theproper techniques.
Figure 2: Diagnostic testing equipment.
We’ll provide diagrams to show how to connect thetesting devices to the vehicle’s electrical components.We’ll provide charts to reveal what are acceptablereadings on the various devices. And as in the preventivemaintenance section, we’ll show you how to safelyperform diagnostic procedures.
The Importance of Selecting the ProperElectrical Components
1.5
In the event that your diagnostic procedures point to afaulty electrical component, you’ll need to carefullyselect the correct replacement component.
It’s not enough to simply replace an alternator or starter,for example, with an identical version of the faulty partbeing replaced. There are two primary reasons why thisis so. First, there’s a chance the faulty part’s specifica-tions never actually met the vehicle’s amperagedemands. Second, the vehicle’s amperage needs mighthave increased over time.
In any case, a new component needs to support thevehicle’s electrical load requirements. This is espe-cially true with newer vehicles’ highly sophisticatedcomputer systems, which need to be closely integratedwith electrical systems components.
Voltmeter
Ammeter
Carbon pile tester
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1.6 The Importance of Following Safety Precautions
We want your vehicle to operate trouble-free. But wealso want you to follow safety precautions whenperforming preventive maintenance and diagnosticprocedures.
Whether you’re working on the battery system, chargingsystem, or starting system, make sure the vehicle’swheels are securely chocked and the vehicle is out ofgear. When working on any of these three systems,always wear safety goggles or a face shield, neversmoke, and do not wear jewelry or loose fitting clothing.
In the battery system section, we’ve listed severalprecautions to follow when recharging batteries. Hereare some additional precautions to adhere to:
A. Always follow the battery manufacturer’s instruc-tions when equipment such as a battery charger or testeris used.
B. Never lean over a battery during charging, testing, or“jump starting” operations.
C. Don’t break “live” circuits at the battery’s terminals,because a spark invariably occurs where a “live” circuitis broken.
D. Keep batteries protected from sparks and openflames; never smoke near a battery. Batteries emitcolorless hydrogen gas, which is extremely flammable;they can explode if they come in contact with sparks,flames, or ashes.
E. Be certain that battery charger cable clamps orbooster leads are clean and making good connections.A poor connection can cause an electrical arc, which inturn can ignite the battery’s gases and cause an explo-sion. Sparks can occur as a result of loose cableconnections, metal tools making contact between thebattery terminals, and metal tools making contactbetween the ungrounded battery terminal and adjacentmetal parts that are grounded. Don’t use the top of thebattery as a tool rest.
F. Do not charge a battery unless you are thoroughlyfamiliar with the step-by-step procedure for using thebattery charger.
G. The room in which you’re charging a battery must bewell-ventilated.
H. Loose clothing shouldn’t be worn around movingparts.
I. Keep in mind radiator cooling fans can be thermo-statically controlled and could turn on at any time.
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SECTION 2: THE BATTERY SYSTEM
2.1
To begin the topic of the battery system, we’ve providedyou with some basic information on how the batterysystem functions.
Each cell of a battery consists of positive plates, negativeplates, and an electrolyte solution. Batteries produceelectricity because of a chemical reaction between thesethree elements.
An Overview of the Battery System
Figure 3: Battery components
In a fully-charged battery, the positive plate consists oflead peroxide (the symbol PbO 2), which is also calledlead dioxide. Each molecule of PbO2 consists of one leadatom and two oxygen atoms. The negative plate issponge lead (the symbol Pb), which may be composed ofan alloy of antimony or calcium. The electrolyte solutionis sulfuric acid (the symbol H2SO4) diluted with water(H2O).
Figure 4: Fully charged battery
When an electrical load is placed on a battery, achemical reaction takes place. The sulfate moleculesin the electrolyte break off and attach themselves to thenegative and positive plates. At the same time, theoxygen atoms from the lead peroxide positive plates gointo the electrolyte solution to join with the hydrogenatoms, forming H 2O or water. The sulfate moleculesmoving to the plates and the oxygen atoms moving tothe solution release energy. This is called the dis-charge cycle.
Figure 5: Fully discharged battery
When the battery is fully discharged, both plate arelead sulfate (the symbol PbSO 4), and the solution iswater. In the charging cycle, the sulfate moleculesreturn to the solution, and the oxygen molecules in thewater return to the positive plates.
Fully charged and fully discharged states are theextremes. Normally, a battery is partially charged orpartially discharged. For example, a battery may be25% discharged, meaning that 25% of the chemicalreaction has taken place and 75% of the battery is in itsoriginal chemical condition.
2.2 The Primary Causes of Battery SystemMalfunction
Before dealing with preventive maintenance anddiagnostic procedures for the battery system, we’regoing to cover certain environmental and usagehandling factors that can cause the system to malfunc-tion.
Excessive heat. When batteries are subjected to hightemperatures, positive plates corrode quickly andbattery cells dry out.www.Be
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Cold weather. Because engine oil thickens in coldtemperatures, it makes engines harder to crank. Thisplaces a heavier and longer-lasting drain on the battery.
Vibration. If a battery is not securely fastened to thevehicle’s frame, the resulting vibration can shed theactive material from the battery’s plate grids.
Fast charging. Using a high charging rate to quicklycharge batteries can be damaging, if the batterybecomes overheated and begins gassing.
Deep cycling. Repeated deep cycling will eventuallycause a battery to lose its ability to accept a charge. Ifbattery cycling occurs use high cycle batteries.
2.3 Preventive Maintenance Procedure
There are six preventive maintenance procedures thatcan help preserve battery life. These six procedures arealso the first steps you should take when diagnosing(i.e. troubleshooting) a problem in the vehicle’selectrical system. The six preventive maintenanceprocedures are as follows:
1. Check cleanliness. If the battery rack is dirty,remove the battery cables first, then remove the batteryfrom the vehicle. Wash the battery rack with a waterand baking soda solution. Flush the case with water,and dry with a towel. If necessary, clean the batterypost and cable terminal with a wire brush or a specialterminal cleaning tool. Wash batteries with baking sodaand water.
Figure 6: Battery hold-down brackets.
2. Check hold-down brackets. Make sure the bracketsholding the battery to the vehicle’s frame are secure. Ifthe brackets are loose, tighten to manufacturer specifica-tions.
Figure 7: Battery terminal locations.
3. Check battery cables. Battery cable connections toterminal should be checked for corrosion and propertightness, and cleaned and /or tightened as necessary.The cables themselves should be checked for swelling,cracking, or brittleness, cables should be replaced asnecessary.
4. Check battery ground cables. The battery groundcables must be securely fastened to the alternatorground. Also be sure that the points where the cablesare connected to the vehicle’s frame or engine block areclean and secure.
5. Check battery case. The condition of the batterycase often indicates whether internal componentdamage or loss has occurred. Telltale signs are swellingand cracking of the case.
6. Check fluid levels (only on non-maintenance-freetypes of batteries). If liquid in the battery is low, addclean soft water or distilled water only. Adding apremixed electrolyte solution will make the sulfuric acidtoo strong and cause the plates, separators, and case todeteriorate prematurely.
2.4 Diagnostic / Troubleshooting Procedures
When trying to find the cause of a problem in a vehicle’selectrical system, you should always begin with thebattery. In performing any diagnostic procedure,refer to the safety information section in the Introduc-tion section 1.6.
It’s critically important for each individual battery to beproperly tested and fully charged. It’s only then that youcan move on to diagnosing problems with the chargingor starting systems. A battery not fully charged willcause all other electrical systems tests to be inaccurate.
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Remember to always disconnect all battery groundcables, at the batteries, before replacing or servicing anyelectrical equipment. After removing battery groundcables verify no voltage is present at alternator outputterminals.
Beyond the visual inspection procedures mentionedearlier, there are three simple steps to testing a battery:removal of the surface charge, determination of the stateof charge, and load testing.
Remove the battery’s surface charge. Electricalcharges on the surface of the battery’s positive platescause a falsely high voltmeter reading. Removal of thisso-called “surface charge” is required on batteries thathave been charged by an alternator or a battery chargerwithin 48 hours. Batteries on trucks that have not beenrun or charged on a charger within 48 hours will nothave significant surface charge.
To remove the surface charge, you’ll need to slightlydischarge the batteries. This can be done by using acarbon pile load tester to load each battery to one-quarter of its cold cranking amps rating for 15 seconds,see Figure 8. Fifteen seconds is long enough todissipate the surface charge from the plates.
The surface charge can be removed by simply turningon the vehicle’s lights - without starting the engine - fortwo to three minutes per battery.
Figure 8: Carbon pile load tester
Test the battery’s state of charge. The second step inbattery testing involves testing each individual battery’sstate of charge. Connect a voltmeter across each batteryand record the readings. Compare the readings to theFigure 9 chart to determine the percentage of charge. Ifthe battery is at 75% or higher, you can proceed to thethird step - the load test. If the battery is below 75%,recharge it. (See charging instructions at the end of thissection). Remove the surface charge, and then test itagain to determine the state of charge. If after recharg-ing the battery, it is still below 75% charged, the batterymay require further charging or it may be unserviceable.
Figure 9
Carbon pile load testing. The third step in batterytesting is to load test the battery. Follow the carbonpileload tester manufacturer’s instructions whenconnecting the tester and ammeter across the battery.Determine the battery’s cold cranking amp rating, orCCA. Divide the CCA rating by two to determine theload. Load the battery for 15 seconds, adjusting thecarbon pile to maintain the proper load. Do not loadthe battery any longer than 15 seconds, as this maycause damage to the carbon pile. At the end of the 15-second load, read the voltmeter and turn off the carbonpile.
Percentage of Charge
12.60 V
12.45 V
12.30 V
12.15 V
100%
75%
50%
25%
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The table in Figure 10 below is used as a guideline forthe minimum acceptable load test results. Notice that asthe electrolyte temperature declines, so does theminimum voltage. This is due to the effect of tempera-ture on most chemical reactions. The battery reaction isslower as the electrolyte becomes colder.
Figure 10
Batteries that pass the load test may be put back intoservice. Fully charged batteries that fail the load testhave lost capacity or the ability to provide electricalcurrent for cranking.
2.5 Battery Charging
When recharging batteries, please follow these importantsafety precautions:
1) Leave the battery charger unplugged until its cables are connected to the battery.2) Charge each battery separately.3) Use the proper charger.4) Charge batteries in a well ventilated area.5) Never smoke while charging batteries.6) Use protective eye wear.7) Do not wear watches or other jewelry.
2.6 Battery Replacement
If you perform regular preventive maintenance onbatteries, and always properly charge and test batteries,you can avoid or reduce the need for costly replace-ments.
However, if your diagnostic procedures point to a faultybattery, you’ll need to carefully select a new battery.The new battery’s “cold cranking amp” rating mustsupport the vehicle’s intended application, or load andduty cycle.
Minimum Accaptable ResultsElectrolyte Temp (F ) Voltage
70° or above60°50°40°30°20°10°0°
9.69.59.49.39.18.98.78.5
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SECTION 3: THE CHARGING SYSTEM3.1 An Overview of the Charging System
The Charging system is an important part of theelectrical system. It provides electrical current for thelights, the radio, the heater, the engine’s electricalsystems, and other electrical accessories. It alsomaintains the batteries in a charged state, rechargingthem as necessary.
In order to properly service the charging system, youneed to understand how it operates. The chargingsystem has three main components: the alternator, thevoltage regulator, and the batteries.
The alternator generates electrical power to runaccessories and to recharge the batteries. It is normallydriven by a belt located off the crankshaft. Mechanicalenergy from the crankshaft is converted by the alterna-tor into electrical energy for the batteries and accesso-ries.
The voltage regulator acts as an electrical “traffic cop”to control alternator output. It senses when the batter-ies need recharging, or when the vehicle’s electricalneeds increase, and adjusts the alternator’s outputaccordingly.
The batteries are a reservoir of chemical electricalpower. Their primary purpose is to crank the engine.They also supply power to vehicle accessories when theelectrical load is too great for the alternator alone.
Figure 11: Wiring diagram
3.2 The Primary Causes of Charging SystemMalfunction
Before discussing the preventive maintenance anddiagnostic procedures for the charging system, we’regoing to cover certain environmental and productapplication factors that can cause the charging system tomalfunction.
Excessive heat. An alternator can become damaged if itoperates too long at excessive temperatures. Damagingheat levels are generated in two ways: when the alterna-tor becomes dirty either externally or internally restrict-ing its ability to dissipate heat from its external surfaceor not allowing air to pass through the unit, and when airducts and heat shields are not replaced after the alterna-tor has been serviced.
Dirt and dust. Charging system components operateless efficiently when buildup of dirt particles formaround wire and cable connection points. Dirty connec-tion points impair the flow of electrical current.
Vibration. If charging system components are poorlyor loosely mounted to the vehicle’s frame, the resultingvibration can damage sensitive internal components. Aloosely mounted component will also diminish theperformance of the important belt drives. This is veryimportant on high powered engines.
3.3 Preventive Maintenance Procedures
The object of preventive maintenance is to identify andcorrect the potential problems before they occur.
There are three preventive maintenance procedures thatcan greatly enhance the efficiency of the chargingsystem’s functions. These three procedures alsorepresent the initial steps you should take when fullydiagnosing (i.e. troubleshooting) a problem in thevehicle’s charging system. The three preventivemaintenance procedures are as follows:
Clean alternator and connection points. Insure that allalternator surfaces are clean to the point that they do nothave a buildup of dirt, grease or dust. Air flow passagesmust also be clear so that air can easily pass through theunit. All connection points must be clean and free fromcorrosion.
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Component mounting brackets. As mentionedpreviously, you need to make sure that the chargingsystem components are securely mounted to theirapplicable brackets; the brackets, in turn, need to bebolted securely to the engine. Again, if chargingsystem components are poorly or loosely mounted,damaging vibration and diminished belt drive perfor-mance are the result.
Tension and condition of belts. You need to alsocheck the belt for proper tension. Caution: be sure theengine is turned off. A loose belt will slip on thepulley and fail to turn the alternator’s rotor. Check belttension with cricket belt tension gauge. Refer tovehicle manufacture’s specifications for proper belttension. Before you adjust it, however, tilt the belt andinspect it for glazing, cracks, or dryness. A worn ordamaged belt should be replaced.
If the belt is in satisfactory condition, use a belt tensiongauge and check the results, see Figure 12. Differentbelt systems use different gauges. Use propertensioning gauge for your application. Then adjust thetension according to the manufacturer’s specifications.
Figure 12: Belt tension gauge
If you replace a worn or damaged belt, the new beltshould be checked for proper tension as well. A newbelt loses 60% of its tension in the first few hours ofoperation. So it needs to be tested under heavy load, andthen retensioned. After a new belt is installed, run theengine - with every accessory turned on - for 15 minutes(this puts a heavy load on the belt). Then check the belttension again and adjust it if needed. Please note thatbelts on high amperage output alternators may needretensioning twice after installation. Further note that ifthe vehicle has a multi belt drive, the belts need to bematched. Finally, in most cases and on most vehicles,belt tension should be tested every 10,000 miles.
3.4 Diagnostic / Troubleshooting Procedures
Timely preventive maintenance of the charging systemshould keep it running smoothly. However, when aproblem does occur, effective diagnostic (i.e. trouble-shooting) procedures will help you locate and correct theproblem quickly and economically. In performing anydiagnostic procedure, refer to the safety informationsection in the Introduction section 1.6.
Any discussion about the electrical system must beginwith the batteries. Before you begin analyzing thecharging system, you must be sure the batteries havebeen properly tested and are at least 75% charged.Otherwise, any electrical tests you conduct on thecharging system will be inaccurate. (Please refer toSection Two of this manual for procedures on testingand charging batteries).
We’re now going to show you how to perform fourdifferent tests specifically related to the charging system.
Alternator Performance Test. Connect voltmeter toalternatore terminals and ammeter to alternator’s positiveoutput cable, per Figure 13. Make sure ammeter is atleast 6 inches (15 cm) away from alternator to eliminatethe possibility of faulty readings. Make sure voltage ispresent at alternator’s output terminals. Start engine andrun it at 1500 RPM’s (operating RPM). Check that allvehicle loads are turned off and reading on ammeter isless than 20 amps. If ammeter reading is greater than 20amps double check that all vehicle loads are turned offand that batteries are fully charged. Record voltage onvoltmeter. Reading should be between 13.8 & 14.4 v fora 12 volt syatem, 27.8 & 28.4 v for 24 volt systems. Ifthe voltage is not within these ranges then try adjustingthe regulator if available. If the regulator can not beadjusted alternator is defective.
Figure 13: Alternator performance test under load
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Figure 16: Recommended wire size chart
Alternator Replacement3.5
Alternator Performance Test Under Load. Keepengine running at 1500 RPM (operating RPM) andmeters are connected per Figure 13. Turn on vehicleloads until 75% of the alternator’s rated output isachieved on ammeter display. Record voltage onvoltmeter. Compare reading to that taking during theAlternator Performance Test. If alternator voltagedrops more than .5 volts for a 12 V system and .7volts for a 24 V system then alternator is defective.An alternative method of putting load on an alternatoris with a carbon pile tester. Connect carbon pile testeracross batteries. Adjust carbon pile until desiredreading is obtained on ammeter. Record voltage onvoltmeter and shut off vehicle.
Alternator Cable Test. To test the positive cableconnect the ammeter to the positive cable from thealternator. Make sure the ammeter is at least 6 inches(15 cm) away from the alternator to eliminate thepossibility of faulty readings. Connect the voltmeter’snegative lead to the positive terminal of the alternatorand the positive lead to the positive terminal on thebattery, see Figure 14. Start engine and set engineRPM to 1500 RPMs (operating speed). Turn onvehicle loads until 75% of alternator’s rated output isachieved on ammeter display. If necessary use acarbon pile tester to apply load on alternator. Recordvoltage on voltmeter. If reading is greater than .5volts check all wire connections and cable conditions.Repair or replace cables and connections as needed.If reading is less than .5 volts cables are good. Turnoff vehicle loads and shut off engine. To test thenegative cable move voltmeter’s negative lead to thenegative terminal of the battery and the positive leadto the positive terminal of the alternator, see Figure15. Run test again. Use Figure 16 for recommendedwire sizes for any cable repairs.
In the event that all of the diagnostic / troubleshootingprocedures point to a faulty alternator, you’ll need toselect a new alternator. Its “amperage capacity” ratingmust support the vehicle’s intended application, or loadand duty cycle.
If the vehicle has had a history of charging problemsand you’ve eliminated failure in the system, you maywant to reevaluate the capacity of the alternator.
When installing a new alternator and retensioning belts,be sure to carefully follow the instructions noted earlierin this section under “preventive maintenance”.
See Appendix A, B, and C at the end of this manual forthe Alternator Sizing Worksheet, Trouble ShootingFlowchart, and Alternator Test Procedure Flowchart.
Figure 14: Positive cable test
Figure 15: Negative cable test
MaximumAvailable Total Circuit RecommendedCurrent Length Wire Size
60-75 amps 16 feet or less #616-25 feet #425-40 feet #2
80-125 amps 16 feet or less #416-25 feet #225-40 feet #0
130-250 amps 16 feet or less #016-25 feet #025-40 feet #00
250-325 amps 12 feet or less #0012-20 feet #0000
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SECTION 4: THE STARTING SYSTEM
4.1 An Overview of the Starting System
The starting system converts electrical energy from thebatteries into mechanical energy to turn the engine over.A malfunction within the starting system will make itdifficult to get the engine running.
In order to properly service the starting system, you needto understand how it operates. The starting system hasfive main components: the ignition switch or startbutton, a neutral safety switch (an option on somevehicles), the starter solenoid, the starter motor, and thebatteries.
When the key is turned in the ignition switch to the startposition, or the start button is pushed, electricity flowsfrom the batteries to the starter solenoid.
Some vehicles are equipped with a neutral safety switch.If the vehicle is in gear when the key is turned, theneutral safety switch blocks the signal to the batteries,so the engine doesn’t start cranking. Otherwise, thevehicle could jump forward or backward when the keyis t urned.
The starter solenoid is an electromagnetic switchmounted on the starter motor. When coils inside thesolenoid are energized by electricity, they create amagnetic field which attracts and pulls a plunger.Attached to one end of this plunger is a shift lever. Thelever is connected to the drive pinion and clutchassembly of the starter motor.
The starter motor is a small but powerful electric motorthat delivers a high degree of power for a short period oftime. When the starter motor is energized it engages theflywheel ring gear and produces torque, which turns theflywheel and cranks the engine.
When the driver releases the ignition switch from thestart position to the run position, the solenoid is deacti-vated. Its internal return springs cause the drive pinionto be pulled out of mesh with the flywheel, and thestarter motor stops.
4.2 The Primary Causes of Starting SystemMalfunction
Before discussing the preventive maintenance anddiagnostic procedures for the starting system, we’regoing to cover certain environmental and productapplication factors that can cause the starting system tomalfunction.
1. Battery charge. A battery having a low / poor stateof charge will place abnormal stresses on the startingsystem. When measuring battery voltage, make surevoltage is 12.4 V or greater.
2. Excessive heat. A starter motor can become damagedif it operates too long at high temperatures. Excessiveheat is generally due to continuous engagement of thestarter. Damage to starting system components canoccur when the starter motor is cranked for long periods(often due to cold weather starts, improperly tunedengine, etc). Starter should operate for 30 secondsmaximum then let to cool down for 2 minutes.
3. Excessive vibration. If starting system componentsare poorly or loosely mounted to the vehicle’s engine,the resulting vibration can damage sensitive internalcomponents.
4. Corrosion, dirt, and dust. Starting system compo-nents operate less efficiently when corrosion forms ordirt particles build up around wire and cable connectionpoints. Corroded and dirty connection points impair theflow of electrical current.
5. Improper use of starting fluid. Overuse and / orextended use of starting fluid places abnormal stresseson starting system components.
6. Defective solenoid. If the starter fails to engage orfails to stay engaged, the pull-in or hold-in coil may bedefective, or the wiring to the solenoid is bad. You needto check the wiring to the solenoid. If the wiring is okthen the coil is defective and you will have to replace thesolenoid.
Figure 17: Starting system
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4.3 Preventive Maintenance Procedures
The object of preventive maintenance is to identify andcorrect potential problems before they occur.
There are two preventive maintenance procedures thatcan greatly enhance the efficiency of the startingsystem’s functions. These two procedures also repre-sent the initial steps you should take when fully diag-nosing (i.e. troubleshooting) a problem in the vehicle’sstarting system.
Engine operating condition. Keeping the engine ingood running condition is essential to ensure efficientoperation of the starting system. Simply put, an enginein poor condition is harder to start, and this shortens thelife of the starter motor. An engine that starts easilyresults in fewer turns of the starter motor, and therefore,a l onger l ife f or t he s tarter.
Wires and cables. For any type of vehicle electricalsystem, it’s important to keep all connection pointsclean. Road dirt and grease create resistance thatinterferes with electrical current flow. In order to getthe necessary power from a unit the size of a startermotor, there must be little or no resistance between thebatteries and the starter motor. In the same vein, youneed to make sure that wires and cables are clean,properly tightened, and of the proper size. Any loss ofcurrent due to poor connections will reduce power of thestarter motor. Clean all connections on a periodic basis.
Employing the preventive maintenance steps we’veoutlined will be extremely beneficial to the startingsystem. There’s also another way to save yourself a lotof time and wrench work: visually inspecting thestarting system’s components for signs of damage.
4.4 Diagnostic / Troubleshooting Procedures
You must also be aware that if the batteries aren’t beingrecharged, there may be a problem in the chargingsystem, which will lead to starting system problems. (Ifthat’s the case, please refer to Section Three of thismanual for procedures on testing and troubleshooting thecharging system). Once you have verified that thebatteries and charging system are working, you canbegin testing the starting system.
When troubleshooting, you always want to strive for themost easily obtainable solution and progress toward themost difficult problems to address. And remember,when replacing electrical equipment, always discon-nect all battery ground cables at the batteries.
Ignition / run switch test. You should begin bydetermining whether the problem is in the ignitionswitch, push button, pilot relay and associated wiring orif it’s in the solenoid and starter motor.
We’ll begin with the ignition switch circuit. Connect avoltmeter between the ignition switch terminal of thestarter solenoid and ground see Figure 18. Havesomeone attempt to crank the engine and record thevoltage. You’ll get either no voltage, low voltage, ornormal voltage, with slow cranking or no cranking at all.
First, troubleshoot the switch circuit. You can test it byconnecting a remote start switch between the batterypositive and the switch terminal on the starter solenoid.When you close the switch, the starter should engage andstart the engine. Again, record the voltage whilecranking and compare it to your first reading. Adifference of less than one volt is not enough to indicatea problem. If there is a difference of more than one volt,however, then there is a problem in the switch circuit.
Timely preventive mainteance of the starting systemshould keep it running smoothly. However, if the startermotor is cranking slowly, or not at all, it’s time todiagnose (i.e. troubleshooting) the starting system. Inperforming any diagnostic procedure, refer to thesafety information section in the Introduction section1.6.
Any discussion about the electrical system must beginwith the batteries. Before you begin analyzing thestarting system, you must be sure the batteries have beenproperly tested and are at least 75% charged. Otherwise,any electrical tests you conduct on the starting systemwill be inaccurate. (Please refer to Section Two of thismanual for procedures on testing and charging batteries.)
Figure 18: Ignition / run switch test
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Use the voltmeter to check each connection, movingbackward through the switch circuit. If your first test ofthe ignition switch had shown low voltage, that mayindicate a shorted starter motor, which would have torepaired or replaced.
If the voltage in your first test was normal, but there wasslow cranking or no cranking at all, that would indicatea problem related to the batteries, battery cables, or adamaged starter.
Solenoid test. Although the reasons for low voltage ornormal voltage with slow cranking are different, theprocedures for locating the problem area are the same.If the solenoid clicks but the motor won’t turn, it meanscurrent is flowing through the solenoid coils but notthrough the main contacts.
Connect the voltmeter to the motor terminal of thesolenoid per Figure 19. If there’s no voltage from themotor terminal to ground (when the solenoid is acti-vated), that indicates the disc isn’t making contact withthe terminals. The solution is to repair or replace thesolenoid.
Figure 19: Solenoid test
Figure 20: Starter motor test, positive cable
Starter motor test. If voltage is present at the solenoidmotor terminal, then the problem is the starter motor orits cabling. If your original test of the ignition (or run)switch indicated normal voltage, but slow or no crank-ing, your next step is to check the motor system and itsconnections.
If the drive pinion keeps shifting out of mesh with theflywheel, then check for a broken or a loose externalground wire on the solenoid. Replace a broken wire orreattach a loose one.
Measure the amp draw with ammeter in either thepositive, see Figure 20, or ground cable, see Figure21, of the starter motor while pressing the startswitch. If the amp draw is excessive, according tothe manufactures specifications, then the startermotor is faulty. Slow cranking or high current drawcan also indicate that bushings are worn because ofan off-center armature. Worn bushings and / or andoff-center armature cause poling and throw off thealignment of the magnetic fields. But, before youreplace the starter, check the condition of the engineto make sure it turns freely. An engine in poorcondition could cause the starter to work harder orlonger. In other words, the starter may not be theproblem. It may be damaged by the engine’s poorcondition.
Voltage drop test. Sluggish cranking may be causedby a very small amount of extra resistance in thecircuit. This may come from dirty connections or bador broken cables. With the voltage drop test, you firstmust check the starter’s positive terminals, then thenegative terminals.
Figure 21: Starter motor test, ground (negative) cablewww.Beam
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Positive cable test. Connect voltmeter, ammeter, andcarbon pile tester per Figure 22. Adjust a carbon pileload tester until ammeter reads 500 amps through to themeter. Note the voltage reading. On 12-volt system,voltage drop should not exceed .4 volts. On a 24 voltsystem, voltage drop should not exceed 1 volt. Turn offcarbon pile tester when test is complete.
Negative cable test. Connect voltmeter, ammeter, andcarbon pile load tester per Figure 23. Adjust carbonpile load tester until ammeter reads 500 amps. Note thevoltage reading. On 12-volt system, voltage dropshould not exceed .4 volts. On a 24 volt system,voltage drop should not exceed 1 volt. Turn off carbonpile tester when test is complete. If the voltage drop is more than allowable, check the
cables and connections. To be sure the problem isactually a bad cable, do the voltage drop test over againusing a jumper cable to parallel the original cable. If thevoltage drop is acceptable, then you know the cable isthe problem.
One final note: There are many variations of groundingthe starter circuit. Some vehicles have a ground cablefor the battery and another ground cable for the startermotor. Both attach to the frame. When doing a voltagedrop test, you must check all cables regardless of thecircuit.
4.5 Starter Replacement
In the event that all of the diagnostic / troubleshootingprocedures point to a faulty starter, you’ll need toreplace your unit with a new starter.
Figure 22: Positive cable test
Solenoid voltage drop test. The final check takes placeat the solenoid terminal. And for this test, you mustcrank the engine. Disconnect the carbon pile load tester,voltmeter (if applicable), and ammeter so that none ofthe testing equipment will be damaged by the testprocedure. An autoranging digital voltmeter is useful inthis case, as full battery voltage appears across thesolenoid terminals before they close. Connect voltmeterper Figure 24. Crank the engine and note the voltagereading. No more than two-tenths voltage drop shouldexist between the solenoid contacts.
The voltage readings from the three tests (Positive andNegative cable tests and Solenoid voltage drop test) mustnot add up to more than one volt for a 12 volt system or2.5 volts for a 24 volt system.
Figure 24: Solenoid voltage drop test
Figure 23: Negative cable test
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SECTION 5 : CONCLUSION
5.1 The Benefits of Using Proper PreventiveMaintenance and Diagnostic Procedures
After having read this manual, we think you’ll agree thatservice technicians who approach their craft as “diag-nostic experts” exhibit a higher degree of professional-ism than mere “parts changers”.
The use of proper preventive maintenance and diagnos-tic procedures has many advantages. Electroniccomponents inevitably last longer and vehicle downtimeis greatly minimized. You will be able to take pride in ajob well done. And your company will be pleased withthe cost savings resulting from trouble free vehicleoperation.
5.2 The Benefits of Selecting Proper ElectricalComponents
As we’ve also noted throughout this manual, carefulselection and replacement of electrical componentsassures that your heavy-duty vehicle’s entire electricalsystem will operate to it’s utmost efficiency.
We at Leece-Neville trust that you’ve found this manualto be helpful. Continue to use it as a reference guide,and refer to it as necessary. Always feel free to contactus with your comments or questions.
Leece-Neville is committed to providing you withreliable, durable, quality built electrical components.And we’re committed to equipping you with theknowledge to perform your important job in the mostprofessional manner possible.
Figure 25: Quality Leece-Neville Starter Motors
Figure 26: Quality Leece-Neville Alternators
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Appendix A: Alternator Sizing Worksheet
CABHeater (Select only ONE) Heater/AC Blower Motor - 4 (high) Heater/AC Blower Motor - 3 Heater/AC Blower Motor - 2 Heater/AC Blower Motor - 1 (low)
Key On All Loads Off (Default 1 Qty) 1 10.00A/C Compressor ClutchInterior LightsMirror HeaterWindshield Wiper (high)Windshield Wiper (low)
Total _________
RADIOSAM/FM RadioCB
Total _________
SLEEPERBunk Fan (Select only ONE) High Medium Low
Bunk HeaterLights
Total _________
Typical Qty Total
Current / Amp Current / Amp
Rating
ACCESORIESMicrowave Oven (Inverter Powered)Electric BlanketSatelliteRefrigerator (Cooler Style)Television & VCR
Total _________
BATTERIESBattery @ 8 amps each
Total _________
Typical Qty Total
Current / Amp Current / Amp
Rating
LIGHTS ON TRACTORHeadlights (Select only ONE) 4 - Hi Beam 2 - Hi Beam
Daytime Running Lights
Clearance Marker Lights LED Light (# of LIGHTS) Incandensent Light (# of BULBS)
Brake Lights LED Light (# of LIGHTS) Incandensent Light (# of LIGHTS)
Turn Lights LED Light (# of LIGHTS) Incandensent Light (# of LIGHTS)
Fog/Driving LampsBack-up LampsTail Lamps
Total _________
LIGHTS ON TRAILERClearance Marker Lights LED Light (# of LIGHTS) Incandensent Light (# of BULBS)
Brake Lights LED Light (# of LIGHTS) Incandensent Light (# of LIGHTS)
Turn Lights LED Light (# of LIGHTS) Incandensent Light (# of LIGHTS)
Fog/Driving LampsBack-up LampsTail Lamps
Total _________
TOTALSCAB = ________SLEEPER = ________RADIOS = ________ACCESORIES = ________BATTERIES = ________LIGHTS ON TRACTOR = ________LIGHTS ON TRAILER = ________
Grand Total _________
Total Electrical Load = ________Total Amperage @ Idle (80% of total elec load) = ________
*Note - amps are all estimated values and should be used as a guideline only values may vary, depending on vehicle
14.00 x ____ = ________11.00 x ____ = ________
5.00 x ____ = ________
0.08 x ____ = ________ 0.30 x ____ = ________
0.50 x ____ = ________ 2.20 x ____ = ________
0.75 x ____ = ________ 2.20 x ____ = ________
15.60 x ____ = ________ 2.30 x ____ = ________ 1.00 x ____ = ________
0.08 x ____ = ________ 0.30 x ____ = ________
0.50 x ____ = ________ 2.20 x ____ = ________
0.75 x ____ = ________ 2.20 x ____ = ________
15.60 x ____ = ________ 2.30 x ____ = ________ 1.00 x ____ = ________
24.00 x ____ = ________19.00 x ____ = ________18.00 x ____ = ________12.00 x ____ = ________
10.00 x ____ = ________ 4.40 x ____ = ________ 2.00 x ____ = ________ 9.00 x ____ = ________10.00 x ____ = ________ 7.00 x ____ = ________
15.00 x ____ = ________10.00 x ____ = ________ 8.00 x ____ = ________
12.00 x ____ = ________ 2.00 x ____ = ________
1.00 x ____ = ________ 1.00 x ____ = ________
80.00 x ____ = ________ 3.00 x ____ = ________ 2.00 x ____ = ________ 4.50 x ____ = ________ 3.00 x ____ = ________
8.00 x ____ = ________
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Notes:
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Form PP-1127 3/2001
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(800) 354-0560 Fax (800) 997-6202
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