I recently replaced the radiator (cracked), thermostat (stuck), and aux fuse (blown) due to overheating problem. This fixed it I thought, but today temp creeped up and aux fans never came on. Later they worked fine, but them stopped working again. The fuse is ok this time.

Does anyone know what all is in the circuit that controls the fans? My manual doesn't show the fans in the wiring diagram for some reason. Is there a resistor and/or a relay? I assume there are 2 sensors and I think that I can find these but I don't know what else.

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Ken Fuller
1990 300E

You really need to go to the PartsShop here and purchase the 124 CD Rom set. I has ALL of the wiring diagrams for your car!!! The diagrams are the best part of the CD's!!!!!

You probably only have the fans working on the high setting. You need the low to work when the A/C is on.

Good luck

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Benzmac:
Donnie Drummonds
ASE CERTIFIED MASTER AUTO TECHNICIAN
MERCEDES SPECIALIST 11 YRS

The fan should show in the diagram as a circle with an "M" inside - signifying a motor. Trace out the line from the thermo switch and it will lead you through a relay (possibly a 5 pin) and out to a circle M.

Keep in mind there are several circle M's; fuel pump, blower motor, starter just to name a few.

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Mike Tangas
'73 280SEL 4.5 (9/72)- RIP
Only 8,173 units built from 5/71 thru 11/72

'02 CLK320 Cabriolet - wifey's mid-life crisis

2012 VW Jetta Sportwagon TDI...at least its a diesel

Non illegitemae carborundum.

Just a thought, but are you sure you bleed the cooling system well. An air bubble will cause overheating and if it happens to be in the area of the temp sensor the fans won't come on. I second the praise of the CDs. They have answered many a question for me.