erractic water temp guage

[acmsal]

My water temp guage works fine on my 78 Silver Ann. until I turn on the lights, both road and head lights. Then the guage needle swings all the way to the right past 250 degrees. If I lower the interior lights till they're off the guage reads accurately. I know I must have a bad ground somewhere, but I don't know where to look. Any help would be greatly appreciated. Thanks.

 

[78SilvAnniv]

have I welcomed you?

I am always happy to see other 78SAs!
I grew up over the Altamont from you in Tracy.
I don't know how to search for solutions for your problem, but someone here will be able to help you out. Very perplexing problem. Sorta keeps you 'driving in the dark'! :L
Silver aka:Heidi

 

[80convertible]

You really need a wiring schematic. Then you can locate both the instrument and headlight ground wires and check them out. Electrical diagnosis is always so much fun!

Regards,

Jim

 

[nstg8r]

My 81 did the same thing, then I took apart the dash to put in a new stereo and I noticed that the connector on the back of the gagues wasn't plugged in all the way. I plugged it back together correctly and it has all worked since. I am guessing the guy that installed the last stereo didn't know what he was doing at all. i have all kinds of things that work since I tore into the dash. I hope this helps