Erratic Coolant Temp readings

[IronJoe]

Hi all,

I'm experiencing odd readings from my coolant temp sensor - the needle will bounce up or down, occasionally reading max temp. When I turn my headlights on, hit a window switch, put on my turn signal, WOT acceleration, anything power-related with the car induces this. If the car just idles or cruises the reading is steady.

I suspect a grounding issue, but IIRC the coolant temp sensor wires go back into the loom so I'm not sure where to look.

Also could this be a bad sending unit? Not my first conclusion but I might have a spare to swap in.

Any help or ideas you all could contribute would help greatly!

[grif900]

If you have a spare, swap the sensor. Iirc it sends a variable ground to the guage ie. one wire.

[Rodentmaster]

I have had good results by..........


tightening the connectors on the back of the instrument cluster and applying a coating of solder to the ribbon. It has been mentioned before that the ribbon will and it does, melt very quickly.

Being a electronic technician, I had some flux, low temp solder and a temp controlled station to use........

BEWARE, IF YOU ATTEMPT THIS, YOU ONLY GET ONE GO AT IT!
If you go to far, you'll be needing a new cluster

[IronJoe]

Thanks guys, turned out to be bad grounds as I thought. Tightened things up and voila, perfect instruments!