I am having trouble with the climate control in my 1985 300D. The fan comes on intermittently and the temperature control is erratic. For example if I turn on the fan before the engine starts it will sometimes run, other times it will stop when the engine starts. Sometimes the heater will blow heat when the engine is operating at low RPM's but as RPM's increase the temperature will drop and heater will only blow cold air. Sometimes the fan will not operate at all regardless if it is turned on before engine start (ignition in on mode) or if fan is turned on after engine start. I have cleaned the fuse box and replace appropriate fuses to no avail. Any suggestions as to a remedy?

Pilot