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Old 05-13-2002, 03:04 PM
Posts: n/a
Lightbulb sensor trouble

I drive a 94 200E, so this info might not be 100%, but worth a look anyway ....

The 110deg sensor on my car went bad. I opened the faulty unit to ascertain what could cause the trouble (destroyed it in the process - but it was shot anyway)

It's a mechanical device for switching the aux fan on at 110 whilst it also houses the resistive element for the temp sensor (a three-pronged sensor with 110 stamped on the side).

What happened was that the switching element broke off inside and fell in such a way as to periodically shorting with the temp probe, whilst sometimes causing a short that popped F7 (the aux fan fuse) !! When shorting to the temp probe I got 120deg + on the display whilst it was OK otherwise ...

changed switch / sensor - all fixed. I pulled the sensor as a last resort when testing for bad wiring to the temp sensor proved nothing. A dead short (i.e. chassis earth on the sensor wire) shows 120deg + whilst no contact shows a cold engine - on the 102 engine anyway.

maybe this helps ...

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