Car is a 2008 vrs BMN. Could someone please explain to me like I'm a dummy, why oh why will air conditioning not engage after I have replaced my compressor, condenser and  o rings? Car has had a regas and the outer temperature sensor had a snapped wire - must have been damaged when removing bumper to gain access to the radiators but I had forgot about it. Anyway, soldered the wire and temperature readings are OK, but air con still won't kick in! I dont even see  an increaso0e in revs when I turn the temperature down to the lowest setting. 

Mechanic said it took all the gas, no leaks, and saw no issues other than the temperature sensor. What would cause it not to engage 🤷🏻‍♀️? 

Does your AC system have a clutch on the drive pulley?

Yes I believe so. Just not sure how it operates as I've read there are magnetic and mechanical? 

 

https://www.ebay.co.uk/itm/375465412308?mkcid=16&mkevt=1&mkrid=711-127632-2357-0&ssspo=s4mp-vlkteq&sssrc=4429486&ssuid=7cWLiTnxRpi&var=&widget_ver=artemis&media=COPY

 

This is what I got and fitted for it. 

I see that there is a reference to rating of 12 volts - is there an electrical connector on the compressor? If there is, it will  be supply for clutch or solenoid valve feed - check that this is being fed when A/C engaged. 

AC compressors are permanent drive and have a shear plate on the front I believe they have 2 styles of plate.

you'll probably find the pully is spinning independently too the shaft.

11 minutes ago, GoudaVRS said:

AC compressors are permanent drive and have a shear plate on the front I believe they have 2 styles of plate.

you'll probably find the pully is spinning independently too the shaft.

^^^ for the Mk3, but I wasn't sure if that was the case for Mk2 AC system.

That compressor does not have a clutch, you can see clearly from the photograph on the listing. They have not been fitted for 20 years now.

 

Therefore you should not expect it to "cut in" or for the revs to drop.

 

VCDS will show a compressor shut down code which will reveal the reason why, low pressure, fans not working, sensor problem etc, if it has none and is showing the compressor as working (ignore the power consumed, that is just a calculated figure) and it is not refrigerating then either the modulating valve (shown in the photo) is stuck, the pulley shear plate has sheared or the alloy splined hub stripped out.

 

The first is unlikely with a new compressor but possible, the second can be checked visually, the third also with difficulty, did the new compressor come complete with pulley and shear plate?

The compressor came with the pulley. As others on here suggested, I am now looking at replacing the pressure sensor as it has been hissing when unplugged. But it's a pain in the neck and I'm struggling to find the right tool. Tap spanner didn't help and I worry I'll snap off the pipe. 

I recently had a new compressor fitted after my air con suddenly stopped working. It still didn’t work so the garage had another look and found the new compressor to be faulty. After a 2nd new compressor it still wasn’t working. The weekend before the next trip to the garage, the oil light started flashing. Got the RAC to check the ECU and although no clue to the oil light fault, it showed an a/c pressure sensor fault. It turned out that the garage had put too much gas in and when the engine heated up, the gas expanded and tripped the pressure sensor. Having removed a little gas, it is now working again.

39 minutes ago, 4004BC said:

I recently had a new compressor fitted after my air con suddenly stopped working. It still didn’t work so the garage had another look and found the new compressor to be faulty. After a 2nd new compressor it still wasn’t working. The weekend before the next trip to the garage, the oil light started flashing. Got the RAC to check the ECU and although no clue to the oil light fault, it showed an a/c pressure sensor fault. It turned out that the garage had put too much gas in and when the engine heated up, the gas expanded and tripped the pressure sensor. Having removed a little gas, it is now working again.

Wow that's impressive 😅 who doesn't like diagnosing a fault. I have now checked that my fault is due to an open circuit in wiring, but I've yet to trace exactly where the wire is broken😕  hundreds spent on new parts to keep the system running, but I do not know if the previous compressor was working and the condenser had no fins 🙈 so I think it was worth replacing them anyway.