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Old 03-26-2002, 09:57 PM
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pmizell pmizell is offline
Benz Zealot
Join Date: Jun 2001
Location: Houston, Texas
Posts: 838
Aux fans not starting when "opening circuit"

Hey folks --

As I understand it, the coolant temp sensor on the M103 head that kicks in aux fans and cuts out AC compressor is an "open circuit" sensor which means when disconnected, the aux fans should come on.

I disconnected mine today with AC running and it did not start the aux fans. It does, however, start high speed aux fans at 115c when connected.

Is this sensor faulty or is there a bad relay switch somewhere?

Thanks as always for any insight!


'91 300E, 208k miles
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