Gauges go to full when headlights on

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wh23g3g

wh23g3g

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On my 65 valiant when I turn on the headlights my temp and fuel gauge go to full. If I turn off the lights while running the gauges read correct. I've had these gauges redone twice by instrument specialties. Plus I added a new headlight switch within the last year. I also bought the updated instrument voltage regulator when I had the gauges redone the second time. So what's wrong here?
 
This is VERY likely a simple grounding problem with your cluster. I don't know if you can access might have to remove the cluster. Add a pigtail wire, and run it over to the dash frame or column support. I don't remember off hand those still have the voltage limiter built into the fuel gauge? That is a 3 terminal fuel gauge?
 
when the headlights are on, the dash light(s) are on & likely there on the dash backside printed circuit it is bleeding over (improperly connected to) the ~5 V output from the plug in voltage limiter in the printed circuit & this puts full voltage to the gauges. Keep the lights off (drive in the daytime!) or pull that wire out of the headlight bakelite connector to disable that circuit ( www.mymopar.com will have the colors/schematics for you) till you solve it . I'd pull the dash printed circuit again & go over it with a fine tooth comb. Holler how it goes.
 
67Dart273 said:
This is VERY likely a simple grounding problem with your cluster. I don't know if you can access might have to remove the cluster. Add a pigtail wire, and run it over to the dash frame or column support. I don't remember off hand those still have the voltage limiter built into the fuel gauge? That is a 3 terminal fuel gauge?
Click to expand...

Sounds like a ground issue to me also.
Like the gauges are getting a full ground through the headlight system somewhere.

It does not sound like an actual gauge issue (just so you know that)
 
Rapid Robert said:
when the headlights are on, the dash light(s) are on & likely there on the dash backside printed circuit it is bleeding over (improperly connected to) the ~5 V output from the plug in voltage limiter in the printed circuit & this puts full voltage to the gauges. Keep the lights off (drive in the daytime!) or pull that wire out of the headlight bakelite connector to disable that circuit ( www.mymopar.com will have the colors/schematics for you) till you solve it . I'd pull the dash printed circuit again & go over it with a fine tooth comb. Holler how it goes.
Click to expand...

Yep, seen it before. The short or crossed connection may very well be in how/where your limiter is attached. It could be at the panels harness connection too. Pics will help
 
This is something that has happened with the car just sitting outside. I haven't had a battery for it in a few months. But when I tried it a few months ago everything was working the way it should. I know there is an extra unused connection on the new headlight switch. Should I make it a ground? The dash harness is a new one from year one.
 
Some wire harnesses included a ground wire for that terminal on headlight switch, where the switch was mounted in plastic, so all replacement switches have it. Adding a ground wire there can only help even if it doesn't cure a fault.
 
No the harness has been on almost a year now. The last time I started the car was probably about 4 months ago and everything was working as it should. So it's something that just happened sitting outside.
 
Have you had any mysterious wiring "smoke" or smell? Auto harnesses are notorious........you get some short.......wire(s) get hot in the harness---------melt and cross together--------and next thing y' know, there's a bunch of stuff hooked to "each other" that should not be.
 
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