Engine Coolant Temperature (ECT) Question

[Mitch90535im]

Having the first problem I've seen with my e34/M30 in a long time (knock on wood). Temperature gauge needle is staying in the blue, but heat is good. I suspect a failing ECT, but I'm a little confused looking at Bentley manual.

I have what appear to be two sensors. One is closest to the driver side and is over where the big top hose from the radiator comes into the thermostant housing. The second sensor (with a blue color) is on the thermostant housing closer to the valve cover.

My question is, which is the coolant temperature sensor and what is the other one's purpose? I want to be sure I order the correct part #.

I'm thinking it's #12 in this diagram. My car doesn't seem to have the 3rd middle sensor (#16).

http://www.realoem.com/bmw/showparts...18&hg=11&fg=35

Also, am I likely on the right path in assuming it's most likely the sensor since I actually have heat and not an thermostant stuck open?

[ryan roopnarine]

iirc one is the dme's temperature sensor, and the other regulates what the gauge tells you. i changed them once, but i don't remember which is which, so i don't want to tell you incorrect information.

[ahlem]

Blue is for the brain, the other is for the heater.

[Mitch90535im]

Anyone else with a differing opinion on what might be causing this, or do you concur that I'm on the right track with replacing the ECT sensor?

[ryan roopnarine]

your thermostat is probably doing it. if you are dexterous (sp?) to get the sensors out easily, change the thermostat first.