Coolant Temp Gauge Headaches

[Z06&E30]

86 325 w/ 64k miles.

Car runs great and does not over heat but the coolant temp gauge does not work correctly.

I have cleaned the posts and tightened the nut on the back of the cluster. I have also 'built up' with some solder on the board since it was a little worn out. I have also replaced the temp gauge with another used unit but still haven't gained on it.

SI batteries have been replaced and I believe thats where the problem is. Prior to the new batteries I had a erratic tach and MPG gauge BUT a WORKING coolant temp gauge.

I don't think the problem is at the thremo since it was working prior to the SI battery replacement.

Hints or info on tackling this?

[dvallis]

Check the brown temp sensor on your thermostatoc valve

[Z06&E30]

Check the brown temp sensor on your thermostatoc valve

What am I checking for? Also which plug on the thermo is responsible for sending the the temp to the guage? There are 4 different plugs. I know the very forward one messes with how the car runs/idles because if you unplug it, it will stumble badly.

[Z06&E30]

Figured it out, did a jumper and deleted the SI board entirely. So far no problems doing so..

[IceWhite]

Could you share what you jumper'ed.

[HerbE30]

could you share what you jumper'ed.

x2

[Downeaster1]

I'm going to be doing it this weekend, and will post a pic/write up if OP hasn't.

[AWDBOB]

Just ended up having to replace the entire SI board with a spare I had.

Si board was failing, causing the temp gauge to read incorrectly. No new gauge, cleaning, etc would fix it, it was the si board itself, with Bavrest's stamp of approval.

[superj]

if you google, there is a write up with pics on what to jumper for certain gage clusters. I think only the early ones can be jumpered but tis been about 12 years since I did one. it used to be on e30tech because I did pics when I did my 84's si board delete

[Z06&E30]

All,

For whatever reason I don't notifications when people respond to my threads or posts, so sorry for the ultra late response.

As superj said, there is a google image out there. I couldn't find the write up. But I've had this jumper wire soldered in place since I posted about it. Temps are normal and I've confirmed by checking with a laser temp gun and closely watch my temps. Going down hill coasting, it will fall. Cold icey weather, slower getting to temp vs a hot summer day.


Here is the image from google, like I said I can't find the write up. My car is 1986 325 auto and the mod worked. I don't know which years are different or not so I can't help there.

[superj]

I did the same jumper on my car.

The little "U" is the jumper. Ignore the skinny red one going upwards bcause that is a repair for a failed circuit