In need of some expert advice here. The compressor seams to be losing power and shutting down randomly. After disconnecting and reconnecting it begins to work again until the car is turned off and then wont reengage. Time for a new compressor or just a control unit thing? Any thoughts would be appreciated.
The first thing is to check the refrigerant charge. Your symptoms correspond to an overpressure safety shutdown usually caused by low refrigerant.
Brett
Watch the auxiliary fan - if that is running so should the compressor - aux fan not running = compressor not running.
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What you are describing still sounds to me like a safety shutdown. You need to monitor both high and low side pressures from a cold start to shutdown to really see what is up.
Brett
I must inject a nuance which is that operations don't care what a technician gauge set says the pressure is, but rather what the controller box thinks it is.
So for this troubleshoot the seasoned technician will be looking primarily at the output of the pressure switches with a 2nd opinion or reference measurement coming in from the gauge set.
IOW's sensing could be funky.
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Probably not related to this BMW case, but some compressors, like on my MBZ, have a compressor speed sensor, to check for slip and overspeed.
In such a case I would be checking for (electrical) noise or drop out.
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Also wondering if any of this sensing or faults would show up on scan codes.
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