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MANUAL AIR CONDITIONING: COLD AIR PRODUCTION

1 Control panel.2 UCH.3 Protection and Switching Unit.4 Injection computer.5 Air conditioning compressor.6 External temperature sensor.7 Resistor unit.8 Passenger compartment fan.9 PTC heating resistance.

10 Engine cooling fan.Vehicle multiplex network.Compressor request (press on AC button).Air conditioning compressor power supply.Engine cooling fan speed signal.AC indicator light control.

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AIR CONDITIONINGAIR CONDITIONING

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The requests to start the air conditioning compressor, coming from the control unit, aretransmitted by means of 3 computers:

- the UCH,- the Protection and Switching Unit (UPC),- the injection computer.

When the user presses the AC button, the control panel sends this request to the UCHby cable. The control panel earths a potential of 12 volts supplied by the UCH. Thisearthing is pulsed. The control panel also notifies the UCH, on another track, of thepassenger compartment ventilation status.

If the ventilation speed is zero → potential 0 volts.

If the ventilation speed is not zero → potential 12 volts.

The UCH then sends a request to the injection computer via the vehicle multiplexnetwork. The latter sends its response, again via the vehicle multiplex network, to theProtection and Switching Unit (UPC). Finally, the UPC provides power to thecompressor clutch.

NOTE

The AC indicator light (incorporated in the AC button) is controlled by the UCH.It comes on when the user presses on this button, even if the compressor startconditions are not satisfied.

Indicator light off → potential 12 volts.

Indicator light on → potential 0 volts.

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CONTROLLED AIR CONDITIONING

1 Control panel.2 UCH.3 Protection and Switching Unit (UPC).4 Injection computer.5 Climate control compressor.6 External temperature sensor.7 Internal temperature sensor.8 Insolation sensor.9 Passenger compartment fan power module.10 Passenger compartment fan.11 Engine cooling fan.12 PTC heating electric resistance.

Vehicle multiplex networkAir conditioning compressor power supply.

In the case of controlled air conditioning, the compressor start-up requests are madedirectly by the vehicle multiplex network.

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THE SENSORS

• Internal temperature sensor

It is a CTN type variable resistor (5 volts). It is located in the base of the interior rear-view mirror. A microturbine (12 volts) is connected to it. The air conditioning computeruses this information:

- to determine the set value of the blown air temperature,- to control the mixing motor,- for the air conditioning demand,- to manage the ventilation speed,- to manage the air distribution.

• Insolation sensor

1 Internal temperature sensor.2 Microturbine.

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This is of the photoresistant type. The supply voltage is 5 volts and theresistance is proportional to the amount of insolation. It is identical to thoseon RENAULT Laguna II and Vel Satis. It measures solar radiation.

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• External temperature sensor

It is a CTN type variable resistor (5 volts). It is located in the right-hand door mirror. Itis connected to the UCH which transmits its value to the vehicle multiplex network. Theair conditioning computer uses this information:

- to request engagement of the compressor clutch,- to manage the recirculation flap,- to control the PTC heating resistances.

• The coolant temperature signalThe injection computer sends this information to the vehicle multiplex network. The airconditioning computer uses it:

- to determine the set value of the blown air temperature,- to manage the position of the mixing flap,- to manage the ventilation speed.

1 External temperature sensor.

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THE ACTUATORS

The recirculation motor is a DC motor. Its supply (5 volts) is timed.

The passenger compartment ventilation motor is a DC motor (12 volts). A computermanages the different ventilation speeds. These are determined by the air conditioningcomputer and are transmitted to this computer by a modulated pulse current. Thepotential (12 volts) is provided by this computer. The air conditioning computergenerates sequential earthing operations.

The mixing and distribution motors arestep motors, without recopypotentiometers. They are reinitialisedautomatically after each battery +interruption, when the ignition is switchedon.

1 Stepper motor.X8

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1 Passenger compartment ventilation computer.

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PTC HEATING ELECTRIC RESISTANCE

Depending on the country versions and for certain diesel versions,RENAULT Mégane II may be fitted with a PTC heating electric resistance. It replacesthe thermoplungers. This resistance, with a power of 1 000 watts, consists of3 separate stages of 330 watts each. These stages are controlled by 2 relays:

- 1 relay controlling one stage,- 1 relay controlling two stages.

R1 Control relay (1 stage).R2 Control relay (2 stages).

PTC power supply.Relay control.

By combining control of one of the two relays or both relays together, the heating powercan be modulated to 330, 660 or 1 000 watts according to heating requirements andthe electrical power budget.

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START-UP CONDITIONS For vehicles fitted with basic heating or manual air conditioning, the start-up conditionsof the PTCs, at full power, are:

- engine coolant temperature less than 50 °C,- external temperature less than 5 °C,- engine running,- passenger compartment fan operating,- injection computer authorisation,- alternator available power greater than 65 %.

If these conditions are satisfied, the UCH controls the 2 relays in 3 stages:

- 1 : operating one relay (330 watts),- 2 : switching off the 1st relay and operating the 2nd relay (660 watts),- 3 : operating both relays together (1 000 watts).

In the event that certain conditions are not met, the power may be modified from660 watts to 0 watts.

For vehicles fitted with controlled air conditioning, an additional condition is necessary:blown air temperature setting.

This temperature setting is calculated by the controlled air conditioning control panel.It is dependent on:

- the value of the set temperature (entered by the user),- the internal temperature,- the external temperature,- the coolant temperature.

From these, it computes a blown air temperature requirement (warmer or colder).

For example, if the user requests a low set temperature (16 °C), the system does notrequest start-up of the PTC heating resistance, as the requirement for warm air is low.To decide this, it uses the blown air temperature setting. If this value is less than 50 °Cthe system does not operate the PTCs.

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For example, if the user requests a high temperature setting (24 °C) with:

- an internal temperature of 5 °C,- a coolant temperature of 10 °C,

the blown air temperature setting will be high (PTCs operated).

On the other hand, if the user requests a high temperature setting (24 °C) with:

- an internal temperature of 23 °C,- a coolant temperature of 80 °C,

the blown air temperature setting will be low (PTCs not operated).

LOCATION OF THE RELAYS

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1 PTC.2 Heater radiator.3 Evaporator.4 Mixing flap.A Air inlet.B Outlet to passenger

compartment.→ Circulation of the air.

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1 PTC relay.

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These relays are mounted on the upper left-hand side of the air conditioning unit, in asmall housing.

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MAINTENANCE

FAULT FINDINGFor controlled air conditioning, there are two types of fault finding:

- fault finding by computer,- fault finding by function.

For manual air conditioning, only fault finding by function is possible (fault finding is notpossible for the control panel).

THE DIFFERENT CONFIGURATIONSWhen replacing the controlled air conditioning computer, it is necessary to configurethe body type (B or J).

When replacing the UCH, it is necessary to configure:

- the type of air conditioning (heating, manual or controlled),- the maximum power of the PTC heating resistances (0, 1 000 watts or

1 800 watts)*,- the alternator drive ratio,- without evaporator sensor,- alternator with DF terminal.

* the 1 800 watts configuration is only used on body type J (MPV).the 0 watts configuration is used when the vehicle is not fitted with PTCs.

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GLOSSARYAC Air conditioning

BFRH Passenger Compartment Relay and Fuse Box

CAN Control Area Network (multiplex communication protocol)

DAEV Electric variable power assisted steering

DF Terminal Digital Field ("available power" signal from an alternator)

EOBD European On Board Diagnosis

ESP Electronic Stability Program

ISO Diagnostic Fault finding via the K and L lines

PTC Positive Temperature Coefficient (electric heating resistor)

RCO Opening Cyclic Ratio signal (mass sequential time)

SSPP Tyre Pressure Monitor

UCH UCH

UPC Protection and Switching Unit

USB Universal Serial Bus (standard computer connection)

VSC Keyless vehicle

VVT Variable Valve Timing (variable distribution)