I've been in the process of putting my 2008 R56 Mini back together after replacing the timing chain, vacuum pump, turbo oil lines, and oil filter housing gaskets. If you've worked on one of these you know you have to basically take the front of the car apart to get access to the exhaust manifold so that you can get to the oil line and oil filter housing behind it.

Well all that "hard" stuff is finished and I'm now putting it back together. I can't, however, get the A/C compressor to turn on. I did not originally open the A/C system and so that was intact. I later determined that the A/C compressor clutch was an open circuit and so I purchased and installed a used compressor. I did check that the clutch was good on that one before installing.

I also replaced the A/C pressure switch which is back near the firewall as well as the A/C compressor relay in the passenger footwell.

I've added the correct amount of R134a but it still does not engage. I'm out of ideas at this point.

Can anyone here give me anything else to check?

  • Did you draw a vacuum on the system prior to adding R134a? Also, how did you put "the correct amount" of R134a in? How did you measure it? Nov 30, 2020 at 23:45
  • Yes, I pumped it down for about an hour with my A/C vacuum pump before adding R134a. But even so, I think it should run the compressor, for a while at least.
    – jwh20
    Nov 30, 2020 at 23:56
  • Did you test the clutch to ensure it is working correctly? You can do this by applying a 12vdc source directly to the terminals without the car running. Also, check the relay which powers it. You can also jump the wires which go to the pressure switch, which will fake the system into thinking there is pressure in the system (vehicle needs to be running for this one). I'll ask again from above, how did you put "the correct amount" of R134a into the system? How did you measure it? Dec 1, 2020 at 15:29
  • @Pᴀᴜʟsᴛᴇʀ2 I did check the clutch itself with a 12V source and it does engage. I did check and replace the relay. I replaced the pressure switch. I determined the amount of R134a by weight. The svc. manual called for 16.9 oz.
    – jwh20
    Dec 1, 2020 at 15:44
  • What is the static pressure in the system? Dec 1, 2020 at 15:59


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