Electrical gauge issue. Never seen this before

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May 16, 2014 | 07:25 PM

Gordonm

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From: Forked River NJ

Electrical gauge issue. Never seen this before

I have been working on this 79 and went for the alignment today. Everything was good on the trip over just ruts and bumps threw the car around. So when I picked it up it drove great. The new Borgeson box working great suspension really improved. Got home and had to go back and get my truck. Girl friend in car heading over, little rain so getting darker. Hit the parking lights. Drive a little look down and the temp gauge is pegged at full hot! Wtf. Car running great no signs of anything. Pull,over and check it seems very cool. Head back home and get the temp gun out. Nice and cool at 185. Wtf. Get the other car and get my truck. Back at the ranch check out the gauge and all looks good. Go out for a ride and temp is back to normal all systems go. Now getting even darker hit the lights and gauge pegs itself again. Lights off good. Now lights on and gauge pegged, turn the dimmer and the gauge goes with the dimmer switch. As I rotate the dimmer it goes up and down with rotation. So somehow the gauge and dimmer are linked. Interesting issue. Any ideas. I know it must be a short or something.

May 16, 2014 | 07:29 PM

Dk Gy Met

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From: New Holland Pa

Just adjust the dimmer to the desired temperature.

(couldn't resist!)

EDIT - actually, mine goes to maxed out occasionally. I think it's a bad connection at the sending unit. Yours sounds like maybe a bad ground in the cluster.
But I'm just guessing - hopefully someone will have a more definitive answer.

Last edited by Dk Gy Met; May 16, 2014 at 07:32 PM.

May 16, 2014 | 08:08 PM

havesometo

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From: Meldrim Georgia

Quote:

Originally Posted by Dk Gy Met

May 16, 2014 | 08:50 PM

'75

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From: McHenry Illinois

Gordon, seems like a poor ground to the gauge. As the gauge lights are turned brighter, there is more load on the ground for the instrument cluster and it begins to fail. Just a thought.

May 16, 2014 | 10:53 PM

wheatpj

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From: St. James, NC

Quote:

Originally Posted by '75

Gordon, seems like a poor ground to the gauge. As the gauge lights are turned brighter, there is more load on the ground for the instrument cluster and it begins to fail. Just a thought.

A poor ground would be my guess too, but it may be somewhere else other than the instrument cluster. I once had a fuel gauge that started pegging (full) every time I stepped on the brake and would return to a correct reading after I took my foot off the brake. There was a broken ground at one of the tail light housing. The tail light continued to work because the circuit grounded though an alternate path shared by the fuel gauge. I guess what I'm saying is if you don't find a bad ground in the instrument cluster be prepared to look elsewhere. Check the wiring diagram.

May 17, 2014 | 08:14 AM

7T1vette

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From: Crossville TN

Sender wire is loose or connection is bad at the sender. It is likely intermittant and the rough road helped initiate the problem.

May 17, 2014 | 08:49 AM

0Willcox Corvette

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From: Jeffersonville Indiana 812-288-7103

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Possibly

Bad headlamp switch ground, or a defective headlamp switch.

Finger on the PCB could be the issue, but the ohms terminal for the gauge is between the power and the ground so unlikely.