I'm in the process of putting my 2008 R56 with 112K miles back together after fixing and common turbo oil line leak and also replacing the cam chain and replacing the seals on the oil filter/cooler assembly which was also leaking.

That part went well and I'm in the final reassembly stages. I did not originally open up my A/C system but when I put the serpentine belt back on and started it up I could not get the A/C compressor to start. After messing around with almost everything I ended up concluding that the A/C clutch was bad, and it turns out it was bad but I'm not 100% sure that I didn't mess it up while trying to get it working.

Fast-forward a bit and I got a used A/C compressor from EBAY which does have a good clutch after testing and I've reassembled and recharged the A/C system. But still it won't turn on the compressor. I've also checked and replaced the pressure switch as well as the A/C compressor relay in the passenger footwell but still nothing.

I'm at a loss here. Any suggestions? Thanks!

 

Hey JWH,

Two things..... make sure your outside temp sensor is hooked up AND make sure your engine coolant temp sensor is literally hooked up because those two sensors are tied to your A/C system. When I did an exhaust valve by removing the front bumper, I removed the outside temp sensor and when came time to put everything back together to start the car up, my AC wouldn't turn on til hooked up the outside temp sensor..... Hope this helps

 

THANK YOU THANK YOU THANK YOU THANK YOU!!!
That was EXACTLY the problem, the outside temp sensor was not connected since I still had the bumper cover removed for easy access to the A/C parts. I plugged it in and the A/C started right up!