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Old 10-21-2011, 12:08 PM   #3
Nervous
Registered User
 
Join Date: Dec 2010
Location: MD, USA
Posts: 1,486
My Ride: 01 330CI 6MT ZSP EU3
Another update. Today morning I started the car, turned on A/C (pressed the snow flakes button), set the coolest temp on it, maximum blower speed, and A/C compressor doesn't engage again.
Actually, after reading a lot about BMW's A/C system, my suspect was evaporator temperature sensor. If it fails, the default value for it will be 0C (32F), at this temperature A/C compressor would not engage. It is located somewhere in left footwell. I tried to heat up that place by heat gun with no success.

Ok, I hooked up INPA and read the errors. No errors stored in IHKA module.
But I found out that INPA can tell you a lot about your A/C. For example, it can show you readings from all the sensors, including the evap temp one. Here is the screenshot while A/C compressor is still not engaged (but snow flakes button is pressed):


As you can see, the reading from the evap temperature sensor is correct, but! The pressure sensor shows NEGATIVE pressure!

After sometime, when engine warmed up (after about 20 minutes), the pressure started to grow, slowly at first, reached + 0.5 (compressor is still off) and then faster and faster and at about 5.0 - 7.0 the compressor finally engaged and then the pressure growth stopped at 11:


I have yet to locate the pressure sensor, plus, I forgot to check the value for the sensor when I turn off the A/C compressor (but after it is already functioned) - I'll do it tonight. After I locate the sensor I'll try to play with it (disconnect/connect, cleanup contacts, heat up with a heat gun, etc). However, it might be a blockage somewhere. What if I connect the A/C gauges when compressor is off, can I use the values of the high side to make sure that there is pressure there? (it actually shows about 150 psi when A/C is off, but I need to measure this again BEFORE the A/C compressor started to work).

Any input is welcomed!
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