Dear Techs...

My 92 400E is overheating due to the external fans not kicking on. I have a bad engine wiring harness, but want to make sure THAT is whats causing the fans to not kick on.

TECHS: Do yall know which Coolant Temp Switch controls the operation of the fans? I know this about the
temp sensors:
One controls climate control
One controls EZL/CIS-E/AKR, and LH
One controls EDS (i think this is the fans)
One controls Coolant Temp Gauge

Is the one that controls the fans the EDS switch?

Thanks guys......Peter

THe blue 2 pole switch controls the aux fans for engine overheating!

M.B. Doc is right its (008 542 45 17) even has a picture of it in the New Fastlane catalog at http://www.peachparts.com/catalog type in the part number and it shows a detail picture that if you click on the picture blows it up even bigger.

With the A/C on, the fans should come on as well. What I see most often is the resistor and the wire burned to a crisp from heat. The resistor and the wire that burns are located behind the drivers side headlamp assy. They are hard to get to, but I'd bet money that are holding back the fans.

The resistor that Benzmac refers to is what the TSB was written about, and described symptoms similar to yours. This is what I had replaced and sits under the alarm systems horn and prevents the fans from coming on.

Hope you find the culprit,
brian W.

Thanks guys...those replies answered my question!

MBDOC: that's the switch located just to the right of the round 4 pole switch right? there's 3 switches in a row. Far left is a 1 pole switch (I figure this is the Coolant Temp Gauge switch), next is the round 4 pole (engine management), and far right is the 2 pole (I think this is it?). Anyway..if thats the one, the plastic is brittle and the wires are corroded to hell, just like the rest of the wiring harness.

Benzmac: Fans aren't comming on at all, A/C or no A/C. I saw the resistor on my ALLDATA printout but never really looked for it on the car. I suspected this is a cause. ALLDATA just told me it was located lower right front engine compartment (lots of help!!!) yeah right. Anyway....I'm going to check that tonight. The relay in the fuse box is good, I even took it apart and cleaned the contacts inside it.

By the way...I caught the fans comming on for a short period last night, but only once, then they shut down and the car overheated again. The car only overheats in stop/go traffic and while at idle, as the main engine fan seems to be fine. Thats why I'm thinking the problem is a darn short in the wiring harness.

Again, thanks for EVERYONES i/p. If anyone has any other suggestions PLEASE let me know. I will be taking it to the dealer next week to start my ******|ng process for a free harness!

Peter