The air conditioning compressor serves to ensure the circulation of refrigerant in the system
The compressor shaft is mounted in the aluminium front cover of the housing on bearings and is sealed on the drive pulley side by a lip seal.
The compressor drive pulley is mounted on a double-row ball bearing and rotates constantly while the engine is running.
When the air conditioning is switched on, the torque is transmitted from the pulley to the compressor shaft through a friction clutch with an electromagnetic drive.
With a serviceable system, when the air conditioning is switched on, a click is heard – the pressure plate of the clutch, under the action of the electromagnet, engages with the drive pulley, and the compressor rotor begins to rotate.
But during the operation of the air conditioning, the following compressor faults may occur.
If, with the air conditioning switched off, the clutch makes abnormal noises during rotation, gets hot or a burning smell appears, its bearing has probably begun to break up.
In this case, the bearing must be replaced.
In some advanced cases, it may be necessary to replace the compressor clutch as an assembly or its component parts.
If no click is heard after switching on the air conditioning, the following faults are possible:
- - a refrigerant leak has occurred, and the control system blocks the switching on of the compressor;
- - the pressure sensor in the system has failed;
- - faults in the electrical circuits of the control system;
- - the winding of the electromagnet coil of the clutch has burnt out;
- - the engine control unit has blocked the switching on of the compressor for some reason (high engine coolant temperature, high engine speed).
If the clutch rotates easily and freely, but when the air conditioning is switched on abnormal noises are clearly heard or the engine even stalls, the compressor is most likely seized.
The internal pumping part of the compressor is not repairable.
In this case, the compressor will have to be replaced.
If a click is heard, the clutch easily turns the compressor shaft, but there is no coolness in the cabin.
In this case, it only seems that the compressor is working, but in reality it is pumping nothing.
Only an experienced specialist with special control and diagnostic equipment can establish the truth.
The cause of the fault can be determined most accurately after a full diagnosis at a specialised service centre for the repair of car air conditioners.
Removal of the air conditioning compressor
We prepare the vehicle for the work
We discharge the air conditioning system, as described in the article – Removal and installation of the heater
We disconnect the negative terminal of the battery
We remove the front bumper (article – Removal and installation of the bumpers)
We remove the auxiliary drive belt (article – Checking and replacement of the auxiliary drive belt)
We remove the lower radiator deflector and unscrew the two bolts securing the power steering radiator to the front suspension subframe (article – Removal of the vehicle subframe)
We withdraw the bushes of the upper supports of the fan shroud from the openings of the upper crossmember of the radiator frame.
Lifting the radiator, we bring the lower supports of the fan shroud out of the openings in the subframe and, having moved the radiator forward in the direction of travel of the vehicle, we place the lower supports of the fan shroud on the subframe.
We press the connector retainer and disconnect the wiring connector from the wiring connector of the compressor clutch.
With a 10 mm socket, we unscrew the three bolts securing the compressor and place the compressor on the subframe.
With a 10 mm socket, we unscrew the bolt securing the pipe flange
We disconnect the low-pressure pipe from the compressor
We remove the sealing ring from the pipe
In the same way, we disconnect the high-pressure pipe from the compressor.
We remove the sealing ring
We withdraw the compressor from the engine compartment
We install the compressor in the reverse order.
We tighten the compressor securing bolts to a torque of 21 Nm.
When buying a new compressor, it is necessary to ascertain how much oil has been poured into the compressor, so that the required amount is poured in when charging the air conditioning.
Replacement of the bearing of the compressor drive pulley
The compressor pulley is mounted on a double-row ball bearing.
When pressed out, the bearing is destroyed, therefore we press it out only for replacement.
We release the refrigerant from the air conditioning system and remove the compressor, as described above.
If the pressure plate is tight and rusted onto the shaft splines, do not try to remove it by inserting a screwdriver into the gap between the pulley and the plate.
This will lead to deformation of the plate.
If necessary, we replace the parts
If the springs are broken or the riveted joints are loose, we replace the pressure plate.
We inspect the surface of the shaft lip seal
If there are traces of oil leakage through the compressor shaft lip seal, the compressor must be replaced.
In some cases, when a leak is detected, the lip seal can be replaced.
But it must be known that the leak is caused by shaft play due to bearing wear or wear of the shaft in the area where the lip seal bears.
It is better to replace the compressor straight away.
If they are worn or damaged, we replace the compressor.
After removal the bearing is no longer serviceable, we replace it.
A slight skew during pressing in can lead to the bearing failing.
After pressing onto the compressor we check the condition of the pulley. It must rotate noiselessly, without jamming, evenly.
There must be no axial or radial runout.
If axial or radial runout is detected during the check, we replace the pulley.
We connect the positive terminal of the battery to the connector of the coil winding, the negative terminal to the compressor housing.
If the gap is not uniform, we replace the pressure plate.
The nominal gap is (0.35±0.02) mm.
After adjustment we unscrew the old bolt from the shaft terminal and screw in a new bolt.
We install the compressor and all the removed parts. We charge the air conditioning system.
Replacement of the electromagnet of the compressor clutch
For the work the following tools will be required: a set of screwdrivers, an 18 mm spanner, pullers for removing the pulley, a puller for removing the electromagnet and a tester
We remove the refrigerant from the system.
We remove the compressor.
We remove the pressure plate
We remove the drive pulley, as described above
To remove the circlip we use a special expanding puller
We shift the electromagnet off the mounting band of the front cover of the compressor and remove it
The resistance must be 3.6-3.8 Ohm.
We install the compressor and the remaining parts in the reverse order.
We charge the system with refrigerant.
