The Stovebolt Site Forums The Shop Area The Electrical Bay Ack, Gremlins! 1967 Chevy dashboard lights

I'm having a confusing problem with my '67 dash lights. All of the gauges usually work right, but when I turn my headlights on, every light on the dash panel comes on(turn signals, high-beam indicator) as well as the illumination lights. All of the electric gauges also bottom out or top out (as if they're getting 12 volts when they should be getting a reading from a resistor). The ground wire to the dash doesn't have continuity to ground, but that doesn't stop the gas and temp gauges from working. The posts on the connector for turn signals and high-beam indicator DO have continuity to ground, except when they're turned on, at which time they have 12 volts. I've been fighting with this until this morning on my way to work, when all the lights on my dash turned off, and my gauges returned to normal.

I replaced my headlight switch, just in case, with no change.

My question is: would a short cause all of this? a malfunctioning relay or solenoid? Or is it more likely that a previous owner screwed around with it and it's actually wired wrong?

Help me Obi-Wan Kenobi, you're my only hope . . .

You must install a working ground wire to the dash. With no ground to the dash, the ground is being supplied through the lamp filaments. The fuel gauge will work until you turn the lights on, then there is too high a resistance to ground for it to work.

GMCPauly,

A pretty perplexing problem. I am not sure this theory could involve all your gauges and indicator lamps, but I'll throw it out anyway.

If one of your taillights or park/turn lights was not able to find a ground in the light assembly, it is possible for it to back-feed through the system and power dash lights as it searches for a ground.

I would check my taillights and any park/turn lights when I had the headlight switch pulled on. Maybe you will see one that is dim...it could be the culprit.

I think this is the way it works!

Stuart

I agree with Baldy. Your dash has a printed circuit behind it. without a good ground it will make everything do crazy things. If it was me I would find out what happened to the ground.
Good luck
Jim

GMCPauly,

The fuel and temperature gauges get power from the dash assembly, but rely on their ground through sending units, not the dash assembly.

It would be interesting to see if your scenario changed when you had the headlights on, but stepped on the brake pedal.

Stuart

Actually, Stuart, you are the one that pointed out the fact that the fuel gauge shows a case ground on the schematics.

I know....you weren't suppose to notice! I think I'm going down for the third time. :confused:

Stuart

Stuart,

You set me straight the other time, so it's a wash. It is good that people come in to correct us when our info isn't quite accurate.