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1990 e30 325i oil temp gauge

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Hi,

Huge fan of the site. I recently purchased a 1990 red bmw e30 convertible. Great car. I read on the site how to properly change the oil and how to reset the oil lights. I followed the directions and have green lights on my dash for the oil. However, the problem i'm having now is that the water temp gauge is on high. With the car off the gauge will be on low but in the second key position it goes to high, prior to the engine even starting. If you BMW geniuses can give me an idea of where to start troubleshooting the issue that'd be great.

Thanks Tim, I wasn't sure which it was.

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that is the water temp gauge not oil temp

Sounds like an electrical issue, im not certain but as far as I know a high temperature reading is a closed circuit so i am guessing you have a short in the wiring or in the temperature sender itself



There are some differences between years but as your car is a 90 I am guessing it will have the single prong brown connector which is the sensor for the temperature gauge only (nothing else, there is another temperature sensor for the engine). Unplug the connector and see if your temperature gauge drops to cold. If it does I would say the sensor has an internal short=faulty.
Also that picture is at idle here is one with the key in the second position.

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Actually i don't think it will be the sensor. I was thinking key in second position is ignition on, but that is third position. I am thinking a short somewhere in the dash or si batteries but will let someone comment who actually knows rather than me guessing.
Also that picture is at idle here is one with the key in the second position.
my cash is on the fact you knocked the sensor, it is on the thermostat housing very close to the oil filler cap.
On the back of the gauge inside the housing there's a small hex nut if that turned loose it could cause it also
Pull off the connector to the temp sender. If you get the same problem it is not the sender. If it is the sender change it. If the problem is still there you have a short to earth somewhere along the wire, or in the instrument cluster. No easy way to find where.
What i meant was the gauges do not have power until the key is in third position (ignition on). This gauge is maxed out with the key in second position. (Notice how the fuel gauge does not have power).
Actually i don't think it will be the sensor. I was thinking key in second position is ignition on, but that is third position. I am thinking a short somewhere in the dash or si batteries but will let someone comment who actually knows rather than me guessing.
Next step

Okay pulled the connection off and it dropped completely. Then I pulled the sensor out and re connected it. It stayed on cold. If it touches the metal edges it shoots back up to the H. Would that just be the sensor or something else? Thanks for everything do far. Super helpful.
If I read you correctly it sounds like the sender is defective. Do check other connections and maybe that nut 'shima 14' mentioned as well.

I think you will find 2 terminals on the sender - one works the needle, the other brings on the overheat light at the red end. Make sure the plug's keyways are not damaged making it possible to fit it the wrong way round.
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