Air Con not engaging A/C clutch

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mnk303

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Just had the system re-gassed and there is no leaks but after this one done I was hoping there was nothing more to do, sadly we soon noticed the compressor clutch did not engage and there was no change in engine rpm on tick over, checked the fuses all ok, not sure what else to do, any thoughts please, don't seem easy to get to the feed on the compressor
 
Drop the lower tray off and you can access the connector to the A/C pump clutch. The clutch is electromagnetic and it has been known for the coils to fail. Use a meter to check the 12 volts is present and if it is then disconnect the conector and check the resistance of the winding. If its open circuit then thats the problem. I think it is possible to replace the coil without removing the compressor and hence degassing the system.
 
Heater fan on at least position 1?

Is the light on on the switch?

Check the relay in the engine compartment fuse box.
 
Darmain said:
Drop the lower tray off and you can access the connector to the A/C pump clutch. The clutch is electromagnetic and it has been known for the coils to fail. Use a meter to check the 12 volts is present and if it is then disconnect the conector and check the resistance of the winding. If its open circuit then thats the problem. I think it is possible to replace the coil without removing the compressor and hence degassing the system.
Click to expand...


Thank you will do, and report back
 
Chaser said:
Heater fan on at least position 1?

Is the light on on the switch?

Check the relay in the engine compartment fuse box.
Click to expand...


Yes done all this, I only regassed it becasue about 2 months ago it was still providing some cold, so something has changed from then, there were no leaks and it regassed right up to 534, so I am going to look more at the connections to the compressor as its not switching in.
 
mnk303 said:
Yes done all this, I only regassed it becasue about 2 months ago it was still providing some cold, so something has changed from then, there were no leaks and it regassed right up to 534, so I am going to look more at the connections to the compressor as its not switching in.
Click to expand...

If it was the clutch coil that was u/s then the engine revs would still rise and the relay could be heard/felt switching in and the light would come on on the switch.

Is all this happening??
 
Chaser said:
If it was the clutch coil that was u/s then the engine revs would still rise and the relay could be heard/felt switching in and the light would come on on the switch.

Is all this happening??
Click to expand...


Nope you cant hear or see andy rev change when you turn the ac on or off
 
Well discovered so far that there seem no drive to the compressor as if we take a live to it it works fine and cools, does this mean there is an issue with the ACU management system as replaced teh relays checked the switch and all ok.
Any advice please
 
After a good look through RAVE. There could be several reasons why the compressor is not engaging.

1. Insufficent refrigerant pressure.

The refrigerant pressure is monitored by what is known as a Trinary switch. What happens is the switch has three states, Low, Normal and High. If the Low signal is present then there is insufficent refrigerant in the system. The compressor is disabled because too little refrigerant means there will be not enough oil travel into the compressor and a risk of siezure.

For info, if the normal switch operates then the condensor fans are demanded to spin at low speed, if the high switch operate then the fans spin up to high speed.

2. Faulty de-icing switch

On the evaporator, the part of the system in the car that does the cooling, there is a thermostatic switch. Normally, if the evaporator temperature reachs -1 degrees C then the switch operates to close down the compressor. Once the temperature has got above +1 degrees C then the switch resets and compressor resumes operation. This is to stop ice forming on the evaporator, which if uncontrolled could damage it. This is the regular clicking you may hear when the air con is operating. If the switch is stuck then no air con.

3. Excessive coolant temperature.

If the engine coolant is reported as above 117 degrees C then the air con is disabled as the engine clearly has too much heat about and needs to unload. The temperature varies between petrol and diesel models but in either case I'm sure you would know if your lump was too hot.


Assuming you are happy that the compressor relay is healthy and all fuses are in tact then the first thing I recommend you do is get your gas pressure checked again. As you have already had the system regassed recently then there is a risk you have lost gas due to the disturbance. If that checks out as okay then there is another component failure.

Report what you find and we'll go from there.

Good luck,

Dave
 
Authoritative response Darmain, i'll be checking mine over at the weekend as my AC is the same (not engaging clutch) i suspected mine is due to low refrigerant as it has never been topped up in 8 years!, maybe a sweepstake on how much is left in is in order!
 
Fake Elvis said:
Authoritative response Darmain, i'll be checking mine over at the weekend as my AC is the same (not engaging clutch) i suspected mine is due to low refrigerant as it has never been topped up in 8 years!, maybe a sweepstake on how much is left in is in order!
Click to expand...


Gas pressure checked and at 530 grams and leak tested under a utra violet lamp, no problems, called several land rover dealers most seems to helpful, but suggested it could be down to teh ECU as there is some feedback controls to this, sad thing is they are talking mega bucks 1000 to £1500, ouch so must try on my own, anyone know a good place in the west sussex area
 
I had the same problem and traced air con clutch power through relays and ECU and found no fault so switched to checking the demand signal to the ECU from the air con switch in the car. I found that this signal was not getting to the ECU, the fault was a broken thermostat (just like a fridge thermostat) inside the car in the passenger side footwell behind the air con unit. Its very difficult to get to but easy to diagnose. there's 2 wires feeding it, seperate single spade terminals, just short together to test. The part is available from Landrover part# LJQL100070 £21.36 although I have not attempted the replacement yet. Anyone else tried to replace this part before would welcome advice. Mine still reunning with it shorted out for now?
 
Been quoted upwards of £1500 by LR dealers, and told by two not to bring it in unless I am prepared to spend this type of money....bye bye LR
 
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