I have a 1985 300SD with 192,000 miles and have been fighting this A/C problem for the past three summers. Some days the air conditioning works just fine but on other occassions it won't turn on (fan or compressor) until I shut off the engine and restart. Sometimes the A/C clutch with turn on and off rapidly and the tachometer will "flutter" and/or "under-report" the true engine speed. Sometimes the A/C compressor and tachometer are completely dead -- revving the engine may or may not bring them back to life.

Any advice you can offer would be most appreciated.

Bill