I have a 85 740 turbo and I rebuilt the motor last december. Last week the temperature guage started acting up. It flickers back and forth once it warms up. I goes between just into the operating range and about 1/3 into the operating range. If it were simply grounding out wouldn't it flicker between registering nothing and the actual operating temp?

If the wires short to ground, the temp goes full HOT.

The warmer the coolant temp, the lower the resistance in the sensor, and the warmer the reading on the gage. Ground = zero resistance (or almost 0)


Mine did this for about 3 months before it just totally died full cold. Use a multi meter to check the resistance across the sensor when it is acting up. If the resistance is jumping all over, just replace the sensor.

I spent about $30 from the dealer (newer 2 wire style on mine)
The gage coolant sensor is under the intake manifold toward the front of the engine. The FI coolant sensor is toward the back (under the intake man).


Brendan
'90 745t m46

Thanks Brendan. I'm going to get a sensor today.

Replaced the sensor, didn't do the job. Anything else it could be. I'm going to look at the connections on the gauge and check the wires and connection for the sensor.

Check the connector that attaches to the sensor . Clean it with some contact cleaner and try to recrimp the connector to make a tighter fit on the sensor. You might even try replacing the connector with a solder or crimp connector. Hope this helps.

I just read the FAQ on the temp sensors. I'm confused. Does my car have 3 different sensors or only 88 and 89? I replaced the in head sensor is there one in the gauge cluster?