91 318i temp gauge not working

[AmuricaEh]

hey so i have a 91 318i and the temp gauge doesn't work at all, every time i turn the car on it just reads full cold and the needle doesn't move an inch at all. I tried checking the temp sensor but thats not the issue. does anybody think it could be in temp sender or the cluster?
Appreciate the help.

[DrJeremy28]

Make sure you have the right sensor. The previous owner bought a cheap aftermarket one for my car and it didn't function properly. Went to the dealer for $54 and it was the correct one. Should be a bit longer than the AM.

[thejlevie]

You can check the gauge pretty easily. With the sensor disconnected the gauge should read full cold and with you ground the connector it should read full hot. If the full hot test fails there is a problem in the cluster or in the wiring between the cluster and sensor.

[AmuricaEh]

ok, il try checking if its the right sensor and troubleshooting the sensor and connector and let you know what happens
thanks for the help

[Gregs///M]

3rd course of action, after the testing above, is to tighten the 7mm nut behind the gauge. Its secures the ground and often rattles loose over the years.

[AmuricaEh]

even if the nut is loose would that cause the temp gauge not to respond at all? cause it just sits at cold even when i drive it. i would figure it could be the thermostat in the housing or the temp sender. but il try it out and let you know.
Thanks for the help so far

[Gregs///M]

even if the nut is loose would that cause the temp gauge not to respond at all? cause it just sits at cold even when i drive it. i would figure it could be the thermostat in the housing or the temp sender. but il try it out and let you know.
Thanks for the help so far

When the gauge sits without moving, it simulates an open circuit or a disconnect in the wiring. With a loose ground (7mm nut) there will be no ground connection, thus an open circuit and your gauge will not work at all. So yea, a loose 7mm nut will most definitely cause your gauge to not move.

The advice given in this thread is exactly what you need to perform to find a solution. So give them a try.

[AmuricaEh]

So it turned out that the previous owner switched the oil sensor with the temp gauage sensor and that wss the cause of why my oil light was on. It fixed the solution to my temp gauge as well. I also removed the instrument cluster and tightened the bolt on the back just to be sure it got an accurate reading Thanks for all the help appreciate it.

[jmaul01]

Know this is an old puts but relates well to an issue we are having at the moment, my son bought a 1991 318i and we are having an issue with the temp gauge not moving other then a very slight up tick at start up. So far we have unplug the temp senor did the ground test gauge went from full cold to full hot, tested ohms across temps senor cold engine 1.202 after 5 minutes running the engine down to .44 and then as the engine cooled the meter gradually started going up. Pulled the gauge cluster the 7mm bolt was loose so tightened (can you tighten it to much... 16 year old son[s car and he is fixing it up he will sit on social media all day but won't search torque specs????). Side note gas gauge grounding nut was missing so he used a zinc plate nut and washer from the hardware store not brass any issues? Back to main issue put cluster back in and temp gauge still won't move. Wire Connector is single brown wire to temp gauge so only one connector in the plug which I am assuming is correct since only one wire out of plug.

Little history on the car it was purchased 4 hours away from our home and he drove it back over three 12k mountain passes it ran great and temp gauge worked fine. When we got home we found the water pipe leaking at the block with a ton of gasket maker around it, replaced o ring and is now good, however we and to remove a far amount of stuff including the plug to the temp gauge to get the pipe out. Also now once the car warms up the check engine light comes on and off as you drive and throws a 1215 maf code. Not sure how the temp gauge issue might be related but is it possible? I am thinking more a vacuum leak somewhere when we put it back together, however the car idles perfect and doesn't bump around at all. Thanks for any help in advance. Jim