300 SEL heater
 

1988 300 SEL. Had no heat. Replaced mono-valve and auxillary pump.

The old auxillary pump was frozen and wouldn't turn when current applied.
Monovalve had torn rubber fitting. I replaced both.

Now neither monovalve nor pump see ground at the proper pin. Does that localized the problem to the push button unit????

Might be the cabin temp sensor but more likely the PBU.

Sixto
93 300SD