On my W124 606 fuel leak fixing project, i just put the intake on and got her back together and cranked her up.

Now, the auxillary fan comes on immediately with key on and stays on. I'm thinking the wiring harness under the intake is shorting somewhere. It really should be replaced as many wires coming off of it to plug into various things have the insulation cracking.

But it worked before. While i'm looking through the electrical manual in fsm finding this fan, does anyone know which temp sensor is the one that would cause fan to go on. I'm guessing the wires going to it are shorted out. Also, i think its the front one right by the fuel filter.

Thanks for any help.

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What Would Rudolph Do?
1975 300D, 1975 240D, 1985 300SD, 1997 300D, 2005 E320 , 2006 Toyota Prius

I have the same auxillary fan problem with my w123.
At least your engine won't overheat.

Lol. Yeah, that thing ran at like 65 C Super efficient cooling fan. I had her fork out the 500.00 for a wire harness. Too much corrosion throughout. Now she'll be good for a while.

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What Would Rudolph Do?
1975 300D, 1975 240D, 1985 300SD, 1997 300D, 2005 E320 , 2006 Toyota Prius

The Aux fan ought to monitor both coolant and refrigerant temps. Hows the AC working?

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Terry Allison
N. Calif. & Boca Chica, Panama

09' E320 Bluetec 77k (USA)
09' Hyundai Santa Fe Diesel 48k (S.A.)