Replace OVP, it's bad, the contact are coming unsoldered. Typical failure. Check the fuel pump relay, too -- if it's hot, replace that before you start having stalling issues.

On the AC, check the belt. If it's worn, the compressor will slip and the KLIMA will kick it out pretty quickly. Also, jumper the wire from the top switch on the receiver/dryer, compressor should come on with ACC wheel set to full cold. If not, it's the KLIMA or the pushbutton unit, if so, it's low on freon.

Slipping belt will cause the KLIMA to kick out and refuse to switch compressor on until you shut car off and re-start.

Check the wires to the compressor too, it's possible, if rather unlikely, that the clutch wire is not connected anymore.

You can also jumper the clutch directly from the battery to test it, it may be faulty. blobs of sticky shredded rubber mean that the shaft seal is leaking and the clutch fell apart, too.

Peter

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1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!