w202 temp gauge doesn't work
 

This seems to be a common issue but none of the simple fixes seem to work. I have a 1995 c36 and the coolant temp has not worked the entire time I've had the car. I bought it with a blown head gasket so I'm guessing this played a role in that.

Up to now I have replaced all the cooling sensors on the thermostat housing and I swapped in a gauge cluster from a different car. Assuming the issue is somewhere between the two how should I go about this? Are there any other common points of failure I should look at?

Does this have the large display HVAC control? If so, you will be able to get coolant temp readings by run engine, turn on blower, press and hold REST, then use the fan speed + - to scroll through the data screen. I think coolant is 05 or 06. If you get a valid reading the sensor is working.

I have the small screen with all the buttons integrated into the wood panel. It is not the w210 style or the one with the knobs. I believe its the earliest style.

That is a very cool diagnostic hack though.

You still should be able to get limited data from that controller, i just don't know how.

Ok. Ill do some research on it then.