Checking the Rear Air Conditioning (A/C)
Checking the rear air conditioning (A/C)
Fault-tracing information
The rear air conditioning (A/C) is activated using the switch on the dashboard environment panel. The climate control module (CCM) then transmits a signal to the rear electronic module (REM) which controls the power to the rear air conditioning (A/C) via a relay.
The only way to regulate cooling output for the third row of seats is to control the fan speed using the blower fan switch.
The front air conditioning, which is controlled by the climate control union (CCM) is directly connected to the rear air conditioning (A/C) using high and low pressure pipes and hoses.
Causes of non-function may be:
- Faulty switch on the dashboard environment panel
- The power stage in the rear air conditioning (A/C) is not working
- The blower fan switch for the rear air conditioning (A/C) is not working
- The fan in the rear air conditioning (A/C) is not working
- The expansion valve in the rear air conditioning (A/C) is not working
- Refrigerant leakage.
Continue - Checking the fault cause
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Checking the fault cause
- Engine running.
Check whether the rear air conditioning (A/C) is not working due to mechanical or electrical faults by:
- activating the rear air conditioning (A/C) via the switch on the dashboard environment panel
- changing the position of the blower fan switch for the rear air conditioning (A/C) between the minimum and maximum positions and checking that the fan changes speed by listening to the noise it makes.
Is the fan working properly?
Yes - Checking the air conditioning system
No - Checking the switch on the dashboard environment panel
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Checking the air conditioning system
- Engine running.
The front air conditioning, which is controlled by the climate control union (CCM) is directly connected to the rear air conditioning (A/C) using high and low pressure pipes and hoses. Check for leakage or for low refrigerant level by lowering the temperature on the climate control module (CCM). If the cooling effect is generally poor for both the front and rear sections of the passenger compartment, the cause of the fault is either leakage or low refrigerant level.
Is the cooling effect generally poor throughout the passenger compartment?
Yes - Checking the refrigerant level and checking for leakage
No - Checking the rear expansion valve
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Checking the refrigerant level and checking for leakage
Check the function of the climate control system. See Climate system, performance test Climate System, Performance Test.
Before working on the air conditioning system, read the safety instructions. See Refrigerant, safety regulations Technician Safety Information.
If the function is not satisfactory and the cooling effect is still cool, leak trace the entire system. See Leak tracing, fluorescent tracing agent / UV lamp Leak Tracing, Fluorescent Tracing Agent/UV Lamp.
Note! The XC90 already has tracing agent in the system.
Check the refrigerant pipe connections in the condenser and in the expansion valves.
Drain the system completely. See Refrigerant, draining Refrigerant, Draining. Replace defective components.
Vacuum pump the entire system. See Vacuum pumping Vacuum Pumping. Fill the system with 1300 g refrigerant. See Refrigerant, filling Refrigerant, Filling.
Check the performance again.
Was a fault detected?
Yes - FAULT FOUND
No - No Fault Found
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Checking the rear expansion valve
Replace the rear expansion valve. See Expansion valve rear, replacing, B8444S Expansion Valve Rear, Replacing.
Was a fault detected?
Yes - FAULT FOUND
No - No Fault Found
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Checking the switch on the dashboard environment panel
- Engine running.
Checking the signal
When the rear air conditioning (A/C) is activated, a signal is sent from the climate control module (CCM) to the rear electronic module (REM). If all conditions are met to activate the rear air conditioning (A/C), for example the engine is running, the rear electronic module (REM) transmits a signal to the climate control module (CCM) indicating that the function is activated. The climate control module (CCM) uses this signal to light the LED in the switch on the dashboard environment panel.
Press the switch for the rear air conditioning (A/C) on the dashboard environment panel and check that the LED lights or goes out
Does the LED light or go out?
Yes - Checking the power supply and ground terminal
No - Checking the switch on the dashboard environment panel
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Checking the switch on the dashboard environment panel
- Ignition on.
Checking the switch
Press the switch for the rear air conditioning (A/C) on the dashboard environment panel. Check that it is working by reading off and changing the status between off and on.
To read off the status of the switch, click on the VCT2000 symbol.
Note! The switches can be placed in any internal order. Select the correct switch position when reading off. Position 1 is the switch to the far left, position 7 furthest to the right.
If the status of the switch does not change, the switch is probably defective.
Remedy as necessary.
Was a fault detected?
Yes - FAULT FOUND
No - Checking the power supply and ground terminal
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Checking the power supply and ground terminal
- Engine running.
Power supply, rear air conditioning (A/C)
The rear air conditioning (A/C) is powered via a relay on the rear electronic module (REM).
Checking the voltage
Check the power supply cable from the battery to the rear air conditioning (A/C). Check for an open-circuit. Check for loose connections. Check for contact resistance and oxidation. Check the fuse. The voltage should be approximately battery voltage.
Ground terminal, rear air conditioning (A/C)
The rear air conditioning (A/C) has a ground input. The ground input from the unit is power ground and is connected to the ground terminal in the car body. See the relevant wiring diagram for further information about the ground terminal.
Checking ground terminal
Check the ground lead between the rear air conditioning (A/C) and the ground terminal. Check for an open-circuit. Check for loose connections. Check for contact resistance and oxidation. With the ignition on, the drop in voltage between the ground connection for the rear air conditioning (A/C) and the ground terminal must not be greater than 0.5 V.
Remedy as necessary.
Other information
- See the relevant wiring diagram for information about circuit and ground terminals in the bodywork
- Checking wiring and terminals Checking Wiring and Terminals.
Was a fault detected?
Yes - FAULT FOUND
No - Checking components
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Checking components
- Engine running.
Checking the blower fan switch
Check that the blower fan switch is working by changing the fan speed between minimum and maximum. If the blower fan switch is working, the LED lights or goes out depending on the selected fan speed.
If the LEDs do not light or go out, proceed as follows:
- check the wiring and connectors between the power stage and the blower fan switch
- check the blower fan switch by trying a new switch.
Checking the engine cooling fan (FC) motor
The blower fan motor is powered by the power unit. The supply voltage must be between 2.5-12 V. If the blower fan motor sticks, the power unit will reduce the power to the fan.
Ensure that the fan is not powered. Check that it is not sticking.
Warning! There is a risk of injury if the fan is powered during this test.
If the fan is sticking, check that there are no objects blocking it.
Check that the blower fan motor is powered as follows:
- activate the switch for the rear air conditioning (A/C) on the dashboard environment panel
- expose the fan and remove the rubber seal for the cable connectors
- using the switch, vary the blower fan speed between maximum and minimum. Measure the voltage between both cable connections on the fan motor.
The supply voltage can vary between 2.5 -12 V.
Note! Do not disconnect the cable connections to the fan motor when taking readings.
If the blower fan motor is powered but is not working, there is probably a fault in the motor.
Checking the power unit
The power stage receives a control voltage from the blower fan switch in the form of an input signal. The power stage uses this signal to control the power supply to the fan motor.
If the fan is not powered by the power unit, proceed as follows:
- check the cable and connectors between the power stage and the blower fan switch
- check the power stage switch by trying a new one.
Remedy as necessary.
Other information
- To access or replace the blower fan motor, see Blower fan motor rear, replacing, R.H.D, L.H.D Blower Fan Motor Rear, Replacing.
Was a fault detected?
Yes - FAULT FOUND
No - No Fault Found
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Fault-tracing information
Information
Fault-tracing information
The fault should have been detected and remedied. As this is not the case fault-tracing has failed.
Exit fault-tracing for this diagnostic trouble code (DTC) or make another attempt.
Do you want to exit fault-tracing?
Yes - Exit Fault-tracing
No - Attempt New Test
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Attempt New Test - Fault-tracing information
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