coolant temp sensor(s)

[greythunder]

hello all, some of you may remember my post a few months ago about trying to test the electric cooling fans on my 92 300d 2.5. it seemed it wasnt hot enough out to give them a test.

Today, after driving the car a good bit, i noticed the temp gauge above 100°c, (see pic below) and the fans were not on.

it get weirder, or more weird or whatever. i pulled the temp sensor(see pic below) harness with one wire, and the engine smoothed out, way out. seemed like i climbed a few rpm's at idle.

then even more weideerer, i pulled the one with two wires, and the fans came right on full blast! WTF!!!?

does this mean both sensors are bad?

keep in mind i had the a/c off, mostly because it's not working right now (taking it for diagnosis on fri)

[Mxfrank]

I think the one pole sensor is for the electronic diesel control, which probably changes fueling based on temperature. Without further research, this one is probably ok.

The two pole switch is a thermistor which senses water temperature for the climate control head unit, which in turn, controls the fans. It's most likely that this sensor is defective. If replacing it doesn't solve the problem, then the CC unit itself may be the problem.

But what is the cause for running so hot? The primary fan is sufficient in most circumstances.

[greythunder]

city driving. it was pretty warm here yesterday and I drove it stop and go for about an hour. then just let it sit idling until the temp started rising. gonna replace the 2 pole sensor soon, we will see if that helps. well, I guess I should just do both to have my bases covered.