I could use some help with my temp gage. I have a 87 Iroc with the 5.0 L engine and automatic. Seems no mater what I do the temp gage is around 245 to 260 while the engine is idling. I have already installed a new temp sending unit and I have replaced the gage in the dash cluster with a used one I had. While I had the dash cluster out I cleaned all the connections as well.

I also rigged up some wiring and jumpers so I could connect directly to the battery and the sending unit. That gage reads 245 as well when my actual water temp is 190 to 200. It's possible both gages are bad since both are used, but I would guess one should read accurate. I also checked the resistance on the sending unit and that reads 185 to 195 ohms as the fan cycles on and off. I installed an aftermarket fan switch that is supposed to cycle on at 195 and off at 185 and it seems close.

I have checked and tested everything that I can think of so any advise will be appreciated. As an added note my oil pressure is bouncing between 30 and 50 psi all other gages seem to be steady and believable. I would like to keep the factory gages but they need to be more accurate than they are. If I cannot make them work I think I might pull the gages and switch to a digital dash.

Thanks for the help.

 

My experience with the factory gauges was that they are not accurate and are more of an estimation. If accuracy is what you seek than aftermarket gauges are in order. That said, does the temp gauge always stay at that temperature or does it slowly go up to that temp and stay around there? If it is always pegged there I would tend to think it is a shorted wire. You could try pulling the gauge cluster and taking a reading with a multimeter off of the connector/tab for the temp gauge. That test should give you a clear indication if it is the cluster or not.

Diagrams here:
http://www.austinthirdgen.org/index.php?pid=19
Specifically scroll down to the bottom for the gauge cluster pin out.

 

Thanks for the info, it is very helpful.

I just fired the car back up after being off the road for several years and the temp guage showed around 250 degrees within a short time of starting. So I put a thermocouple in the water stream and that is showing me 190 to 200. As far as accuracy goes, within 10 to 20 would be fine. Being off by 50 degrees seems to far.

I think my best bet might be to add an aftermarket gage for temp and oil pressure. Then I will have something that I trust. First I plan to clean up and reattach all the grounds from the engine.

 

Have you examined your printed circuit board? If you aren't familiar with it, it's what is attached to the rear of your gauge pod. If yours has corrosion and/or rips, it will cause problems for your gauges.

In this thread, I posted two links/websites to where you can acquire a new one: https://www.thirdgen.org/forums/afte...uit-board.html