Does anyone have a link to one, in particular I'm confused about the various coolant sensors and which is linked to what, i.e. the temp gauge, the fan and the ecu/fueling. I was going to try changing the sensor linked to the ecu but am not sure which it is.

Kind regards

Chris

Why all the secrecy about year and model?

Sorry!!

My car is 1990 300 ce, M103 engine.

Cheers

Chris

Where are you that a 90 coupe has a 103 motor? MB service CDs have wiring diagrams but U.S. versions aren't going to have that specific car, although the 88-89 is likely to be similar. You can sometimes figure out what's what by looking up the parts on parts sites.

I'm in the uk so I guess the specs are a bit different/behind, you lot always get the technology first!

My '91 M103 has a 4-pin sensor on the far back of the head, just above where the intake runners enter the head. going in a circle, pins 1&3 are one temp sender, and pins 2&4 are the other one. Don't know which one is the temp gauge and which is the ECU signal though. But you could pull the connector socket loose and hang a 1K-ohm resistor between the wires going to 1&3 or to 2&4 and see if the temp gauge reads about 40 degrees C. Then you will know by default which two pins go to the ECU.
Each sensor should read approx 2K ohms at 20 c, and 300 ohms at 80C.
Hope this helps, I couldn't find a schematic that specifically identified the pins.
Of course, yours may be totally different.

DG

Cheers for that, should be useful, I'll give it a go this weekend.

Thanks again

Chris

4 pin is engine management
2 pin is aux fan
1 pin is temp gauge

__________________
A Dalton

Thanks Arthur

Cheers

Chris