Ah ha! A clue!

My climate control turns heat on before there is heat. Usually about 1 minute after starting the car. There is no heat available until about 5 minutes though. Not sure why the 1 min delay, but definately doesn't wait to come on until it's warm.

Last year I straightened the fins and cleaned the radiator, replaced t-stat, and water pump. Radiator is only 5 years old.

Still wonder about the circuit for the aux fan. Why won't grounding the sensor turn on the fan? Is there a 2nd relay just for the t-stat sensor? Doesn't make sense.

Anyone know for sure?

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1984 300Sd 210k

Former cars:
1984 300D 445k (!!) (Strider) Original (and not rebuilt) engine and transmission. Currently running on V80 ( 80% vegetable oil, 20% petroleum products). Actually not, taking a WVO break.
1993 300d 2.5 275k. Current 120/day commuter
1981 300SD 188k (Hans) Killed by a deer