230E 1984 Fan Switch

Hi I have a 230E that I am trying to solve overheat fault for a friend, I found that the magnetic radiator fan did not seem to cut in when idling and gauge shows 100'C.
Took out switch in head, found it was a pirate switch made in Italy and showed temp of 85'C. Tested switch in boiling water with multimeter - no continuity at all. Bought second hand switch from scrap yard, original merc but is stamped at 100'C. Tested and found working in boiling water but only after quite a while. Installed in motor and tested. Car reached 80'C while driving and then 100'C at idling quite a while but fan still did not cut in. Ambient is pretty cold now so maybe it needs a higher ambient before it cuts in. Any advise please. James
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My car (1986 190e) has a 110degree sensor. This is an item I would buy new, rather then at the boneyard. you can test the fan's function just by grounding the sensor (you know this, but others may not).
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Yeah, just grounding the sensor should activate the magnetic clutch (i.e. fan is hard to turn by hand. Oh, make sure engine is NOT running :-). If fan is loose, check if there is voltage on the clutch socket. If there is 12v, the clutch is bad.
Martin Joseph wrote:

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