Hi Guys!

This is a great forum!!

Here's what I know about my 89 B280F:

1.) Temp-sensor for the gauge is in the back of the engine, driver's side. Two wire, gray connector.
2.) Temp sensor for the ECU and for the ignition computer is in the thermostat housing near the water pump in the front. (black connector, like the one used for injectors)
3.) Knock sensors are in the middle under the V-shaped water rail.
4.) Oil-temp sensor is the oil drain plug at the same time.
5.) Temp switch which turns on the AUX-fan if the readiator gets to hot.

I found a sensor or similar on the lower portion of the engine near the front on the passenger's side. It is a one wire sensor and has a black wire attached.

It measures almost 0 Ohm to ground and after starting the engine the voltage jumpes almost imediate to +Ub. Stopping the engine causes 0 Volts again. So it seems as the sensor is powered only while the engine is running which makes sense. What does not make sense to me is the fact, that the sensor measures almost 0 Ohms and still achieves Ub when the engine is running. Looks like an thermo time switch, doesn't it? But I am pretty sure it is not a time switch, since it has the LH 2.2 and not even a cold start injector. 0 Ohms are even while the engibe is hot (Florida, like 200 degrees regarding to the oil-temperature).

I am pretty sure it is not some kind of a over temperature cut off switch for the AC either (This switch would actually make sense, but then it should not jump to 12V when the engine is running). If I detach the cable and turn on the engine, the AC is still working.

So what it is for?

The reason why I am asking is I have a pretty high fuel consumption and I changed pretty much everything already including brand new injectors which did not make any difference, although I had a problem with the connections of the knock sensors.

I appreciate any input!!

Gerold