AC cooling problem

[Berglund]

Hi
During the dummer I have had some problems with my AC on the 500e.
When I start the car, or the AC when driving,
the AC turns of for about 1minute or less.
The compressor turns of.
If I stop the engine and restart a few minutes later, the same.
The AC compressor starts, and cooling, and turn of after about 1 minute or less.
The AC pipe get very Cold and it’s cooling the cup’e when it runs. The AC system is full, at full pressure.
There most be a sensor that is defective, why else would it turn off?
Could it be an electric circuit in the compressor, defect?
Could there be an overheating protection that turns the compressor off?
In that case, maybe the sensor is defect….
It doesn’t matter if it’s 15 or 28 degrees Celsius, the same issue anyway

Any ideas on what could be wrong,
what we can troubleshoot?
Is there an electrical diagram available on this forum?
Early-91, Japan-spec

Best regards
Niklas

 

[gsxr]

Niklas, have you checked fault codes on the BM/GM (pin #8 on the diagnostic port)? See if there is code 6 or 7. This indicates the belt is slipping, and the module is shutting off the AC compressor because it thinks the compressor is seized/locked.

If there are NO fault codes, it may be something else. The compressor control system is quite simple, there are not many possibilities to cause this. If the pressure switch sees pressure either too low or too high, that will turn off the compressor.

Electrical diagrams are in the factory manual, Group 24, click here. Scroll down to "83-6.00 - Air Conditioning (A/C), Engine 119 with LH-SFI".

 

[Berglund]

Hi.
Thanks for fast reply
I will check this code and the rest of the description

 

[emerydc8]

If no problems with the belt slipping and pressures are normal, a bad base module has been known to cause intermittent compressor engagement. In my case, turning the engine off momentarily and restarting would usually allow the compressor to engage again, until next time. Before I knew what was causing this, I got good at restarting in neutral without having to pull over and stop. A bad base module is further down the list of suspects for compressor not engaging, but if you have a spare module it doesn’t cost anything to try.

If the system is overcharged and it’s a hot day, the overpressure switch on the receiver/dryer could be tripping the compressor.