On my 87 260E, the temperature switch closes at temp > 105 degC, and this closed switch causes the relay unit to cut off the compressor. Closing the switch grounds the compressor relay unit's pin 12. My sensor has 3 pins, and two switches in the same part. The other switch is for the blower, and that too closes but at 115 degC to start the fan.

So I am assuming that this is the same for the car here.

I had a similar problem, and disconnecting the connector from the sensor got the compressor running.

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Saumil S. Patel