My 2003 VRS has lost its A/C. Last week it was fine, now nothing. When I bought it, the compressor was noisy, squealing when running, but still producing cold air. Got in it last week, and nothing - no A/C whatsoever, and no squealing, so I figured the compressor had given up

I have changed the compressor today for a second hand one, and had the system re-gassed. There are no leaks, and it holds pressure. The compressor isnt engaging, and there is still no cold air. Putting a multimeter to the compressor wiring, I get 7V in the supply. I have checked the fuse in the side of the dash, and all the other fuses. NOthing is blown. I am out of ideas now, and need the A/C back asap as we have a baby due 3 weeks today, so need to be able to control the car temperature.

Any suggestions please?

There is a 4-pin connector that slides into a plastic bracket on the starter motor. Check for bad connections.

If this is a compressor with a magnetic clutch, the squealing would be the clutch plate slipping on the compressor pulley caused by low voltage. If you apply 12V direct to the compressor clutch, does the a/c work?

A faulty fan controller can also cause this sort of problem. Do the radiator fans come on with the a/c?

Going to run 12v to the compressor tomorrow, to see if it kicks in, and cools. If it does, I have electric problem to compressor. If not, compressor may be shot?? God I hate A/C

Rad fans not coming on with the aircon either - noticed that when we re-gassed it.

Check the fuses on top of the battery. The fan control unit is fed by two of the fuses on top of the battery - the third of the bolt down fuse links and the green fuse nearest to them.

All fuses checked and ok. Put a 12v feed direct to the compressor and it works - engages clutch - so im happy at that. There is no power on the compressor feed, or on the 4 wire multi plug near the battery. I have to find the pressure switch now and check power into that - any ideas where it is??

Get it to the garage to check-out for a diagnostic/check-out to find what is wrong.

Tell them what you have done so far and let them take-it from there.

At least you will be on the right track as to what needs replacing or fixed, with the minimum of cost.

You maybe able to fit a new part yourself, at least your not buying stuff you perhaps don't need.?

Good Luck

It should be easy enough to diagnose. Do you have a 10-pin or 14-pin connector on the fan controller?

Once I know that, I can tell you how to test it.

It should be easy enough to diagnose. Do you have a 10-pin or 14-pin connector on the fan controller?

Once I know that, I can tell you how to test it.

Tell me where to look - on the back of the climate control unit? Am sat in the car now lol

I have found the pressure switch - checked it and i get 12v on one wire all the time, nothing on others whether A/C on or off

SPeaking to the bloke who re-gassed it, he didnt completely fill it as the comressor wasnt working., only filled it to leak test it. He seems to think that because the compressor didnt work, he cant fill it, therefore the system reads low pressure and wont run the compressor to stop it burning out? I know it works as I have put 12v to it and clutch engages. He wants to run the compressor on override with my wiring, then fill it from there. he reckons this will allow him to fill it and that will stop any low pressure faults?

Edited 7 July, 201213 yr by broken biscuit

Tell me where to look - on the back of the climate control unit? Am sat in the car now lol

I have found the pressure switch - checked it and i get 12v on one wire all the time, nothing on others whether A/C on or off

SPeaking to the bloke who re-gassed it, he didnt completely fill it as the comressor wasnt working., only filled it to leak test it. He seems to think that because the compressor didnt work, he cant fill it, therefore the system reads low pressure and wont run the compressor to stop it burning out? I know it works as I have put 12v to it and clutch engages. He wants to run the compressor on override with my wiring, then fill it from there. he reckons this will allow him to fill it and that will stop any low pressure faults?

Under the bonnet. As you look at the front of car, it's to the right of the radiator at the level of the battery tray.

It will look something like this (this is a 14-pin one)

 

Exactly as per your picture, with 14 pins on right plug. Was bolted under batttery tray. What a pig to get to

Had to remove battery to get it out

Ok, the system has been re-gassed. when the compressor is hard-wired, I get cold air, and all is well. The problem is clearly an electrical one, as no power is getting to the compressor. Any ideas on that front? At least i know theres no leaks and the compressor is good.

I have now given up - after re-gassing, and running for 5 minutes, the clutch burnt out on the compressor - clearly broken when I got it. I now have to de-gas the system, remove and replace the compressor, re-gas and then try to find out why theres no power to the compressor. If anyone can shed any light on this, it would be very much appreciated. As it stands, the car is going to be going to an auto electrician to source the fault and rectify if i cant do it. Another massive expense. I can't really do without the A/C as I have a baby due in a fortnight and need it for transporting the baby around.

You don't need to degas to change the clutch coil on the compressor - you can do it in-situ. As you didn't get the fans to come on, I think your initial (and current) problem is a faulty fan controller. If you still have the old compressor, you can move what I suspect is a working clutch to the installed compressor.

Wow- thats a result. I shall be scrapyard hunting this week to find several fan modules, and try to get another clutch too, as my old one was noisy. I know how to get them off, so that will be a result. I guess its a bit tight to change the clutch in situ, but better than removing the pump and gassing it again.

Wow- thats a result. I shall be scrapyard hunting this week to find several fan modules, and try to get another clutch too, as my old one was noisy. I know how to get them off, so that will be a result. I guess its a bit tight to change the clutch in situ, but better than removing the pump and gassing it again.

Your old one was probably only making the noise, because the fan controller wasn't supplying enough voltage to hold the clutch plate tight against the pulley.

I will get a clutch unit, and a couple of fan control modules, try the modules and see if i get power to the compressor. if so, i will connect the compressor and see what the clutch does. I know the compressor fitted is working ie generating cold air, as we tested it. If i can get the power there, I know i can get the clutch issue sorted. Thankyou for your help - I am determined not to end up paying a fortune to get this fixed!

Today I have replaced the fan control unit. I now have power down to the compressor - approx 9v. I have plugged the compressor into the loom, and checked it compressor-side of the joint. I get 0v down to the compressor. remove the earth side of the loom from the compressor and I get the power back (hope that makes sense). Whatever I try, the compressor is still not engaging. I know this compressor is good, as I have just put 12v into it, and it works. Something somewhere is not right, and i have no idea now. Any ideas??

Today I have replaced the fan control unit. I now have power down to the compressor - approx 9v. I have plugged the compressor into the loom, and checked it compressor-side of the joint. I get 0v down to the compressor. remove the earth side of the loom from the compressor and I get the power back (hope that makes sense). Whatever I try, the compressor is still not engaging. I know this compressor is good, as I have just put 12v into it, and it works. Something somewhere is not right, and i have no idea now. Any ideas??

You have a bad connection. A multimeter will show voltage as it is high resistance, but as soon as you start drawing current the voltage drops. Try applying 12V at the 4-pin connector by the starter motor. If it works, then the fault is upstream of the connector.

So put 12v down the loom to the compressor at the 4 point connector? Will I then not run the risk of burning out the clutch on the compressor as happened when I put 12 v into the compressor plug? If im following you, if I get the compressor engaging the clutch, then the power fault is back up the loom past the 4 pin connector. I have replaced the fan control unit with one from the breakers, and have a spare low pressure switch i can try if necessary. If its not the 4 pin plug, I have no idea where to go from there.

So put 12v down the loom to the compressor at the 4 point connector? Will I then not run the risk of burning out the clutch on the compressor as happened when I put 12 v into the compressor plug? If im following you, if I get the compressor engaging the clutch, then the power fault is back up the loom past the 4 pin connector. I have replaced the fan control unit with one from the breakers, and have a spare low pressure switch i can try if necessary. If its not the 4 pin plug, I have no idea where to go from there.

Yes, you only need to apply 12V long enough to see if the centre nut on the compressor is turning.

Yes, if that works, then the fault is between that connector and the fan controller.

Ok. Checked. 12v in at the 4 pin connector to the compressor engages the clutch, and i get cold air. Gas is present, and that side of the system is working. This is definitely electrical. Any way of testing further back up the wiring?

Yes. Refer to the diagram, but IIRC the output to the clutch is at pin 10 of the fan controller. Go by wire colours. Disconnect the 14-pin plug from the fan controller and apply 12V at that point. If that is OK, then we know that the problem probably lies with a sensor (IIRC, there are four). Your starting to eliminate things in a methodical way - you will get there

12v into pin 10 engages clutch - wiring from control module to compressor is fine