Temp guage goes higher when switching headlights on...

[Fiat88]

Was wondering if anyone can explain why when I turn the headlights/dash lights on the needle on the temp guage goes higher? Kind of annoying, is that normal and if not, what might be the issue?

[jimincalif]

That was a dealer-installed option!

Mine does too, there's been a couple of threads on this I think. When the lights are on, there is more current flowing into the gauge for the light, and over time the resistance on the gauge ground connection builds up due to corrosion, vibration, etc. More current and poor ground leads to more current thru the sender and a higher reading.

Someone here fixed theirs, pulled the gauge and installed a separate ground connection for the light.

[Fiat88]

Jim, that's what I figured, more current going through the guage. When I replace my dash eventually with a new one, I'm gonna clean all the gauge contacts and wiring, maybe it will help.