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Re: AC Compressor over-pressure relief valve question. Posted by Gary Stottler [Email]  (#1463) [Profile/Gallery]
(more from Gary Stottler) on Mon, 24 Aug 2015 04:19:34
In Reply to: AC Compressor over-pressure relief valve question., Gary Stottler [Profile/Gallery]
, Mon, 17 Aug 2015 07:23:20
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Following up on my AC Compressor issues, I was able to answer the questions I had, maybe the info will help someone else:
1) The Pressure Relief Valve reseats itself and the compressor was not damaged by the overpressure - once everything else was straightened out it worked fine. I believe that I had a plugged receiver/dryer which caused the overpressure situation and also an electrical problem which prevented the compressor from engaging even briefly.
2) Electrically, the Trionic 7 ECU gets an "AC Request" signal from the DICE over the I-bus, and the Trionic turns on the AC relay which engages the clutch. The AC pressure switch and the evaporator temperature switch go into the DICE and have to be in range before the DICE will ask the Trionic to engage the clutch. The Trionic ECU also controls the cooling fan hi/lo based on the AC pressure input from the DICE. My tech was able to look at all those inputs with the Tech 2 scan tool, I have not tried other generic scan tools to see if you can see the AC info in the DICE or not.
3) FWIW, the main electrical issue was that in this car (manual climate control), the resistor pack which controls the cabin fan had failed (apparently this is common) and as a result there was no power going to the AC switch on the dash, so even if everything else in the AC system was fine the system would never get the signal to turn on.
Bottom line, replaced the cabin fan control resistor, replaced the receiver/dryer, and recharged the system and now the system works fine.
Gary
_______________________________________ Gary Stottler
, Mon, 17 Aug 2015 07:23:20, Mon, 24 Aug 2015 04:19:34 <-- Viewing This Message
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