1980 300D. Working aux pump, newer aluminum body servo.
Assumed working (not fried) control module behind glovebox.

New A/C compressor and several replaced vacuum pods.

So worked great all winter. Cabin stayed warm when it should.
A/C does cool off car, worked good at end of summer last year.

Noticed that when A/C compressor is switched off that cabin vent
air is hotter than outside air.

Unplugged auxiliary water pump (was going to put a ball valve on the
water line next) and noticed cabin cooled off and vent air is now same
temp as fresh air outside.

My assumption is that aux pump should stay off when heat is not needed.

So, anyone have a similar problem and solution ?

Anyone have the short and easy method for testing the ambient temp sensor,
cabin sensor, and sensor in the air box ?

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80 300D 340K Owned 30 yrs
83 300SD 440K Owned 9 yrs - Daily Driver 150mi/day
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