Temp Sensor Pegged

[Deah7]

Hey Everyone,

I purchased a 91 318is swapped with an m52. The temp sensor immediately pegs the second you turn the key even if the car hasn't been cranked in a week. I am curious if anyone has any clue what might be the problem? Wrong sensor, bad ground, wrong wiring, etc. The second sensor under the intake manifold looks like a single pin black sensor. Any help is appreciated.

I did search but I couldn't find much information on what causes the needle to peg. Most things I found were about the sensor not working at all.

[ian e30 318is]

It's most likely either a bad ground or bad sensor. The ground could either be in the cluster or the sensor itself on the head (brown top sensor). The blue top sensor will be coolant sensor for the ECU onless you are running with an OBDII car in which the sensor I believe is black.

[vpilarrt]

The sensor wire could be damaged and touching ground somewhere.

[Deah7]

Thanks for the responses. I'll look into it this weekend!

[Deah7]

It's most likely either a bad ground or bad sensor. The ground could either be in the cluster or the sensor itself on the head (brown top sensor). The blue top sensor will be coolant sensor for the ECU onless you are running with an OBDII car in which the sensor I believe is black.

When you say in the cluster itself how common is this? I've diagnosed it further and if I unplug the blue C1 connector from the back of the instrument cluster the temp gauge still reads full hot so I'm assuming it is grounded inside the cluster itself somehow. This seems to be the only logical reason but since I have never heard of this happening I am second guessing myself.

[sweet3]

Make sure your cluster temp sensor is the Brown e30 single pin sensor.
Also, double check to make sure you didn’t get the oil pressure and the cluster temp connectors mixed up

[Gregs///M]

Yes, the 7mm nut behind the gauge is either missing or loose. Try tightening it. If the problem is still there, you will need a refurbished main circuit board and SI board.

[e30m20TurbO7]

i had this problem, it ended up just being the gauge

[Adrian_Visser]

Yes, the 7mm nut behind the gauge is either missing or loose. Try tightening it. If the problem is still there, you will need a refurbished main circuit board and SI board.

Where does one find a refurbished main circuit board? My coolant temp gauge flicks around and I'm pretty sure the problem lies in the cluster itself.