1973 headlight switch- gauge lighting?
Thread Starter
Burning Brakes
Joined: Jun 2005
Posts: 1,130
Likes: 106
From: laingsburg MI
2020 C3 of the Year Finalist - Modified
1973 headlight switch- gauge lighting?
I just realized that my center console gauges turn OFF when i turn the head lights on. They turn on and off with the key. The speedometer and tach light up as they should. Suggestions?
Le Mans Master
Joined: May 2003
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From: Fernandina Beach FL
2023 Restomod of the Year finalist
2020 C3 of the Year Winner - Modified
What do you mean by center gauges turn off? Which ones?
So you have the car ignition on not acc- the gauges work- but when you turn on the headlights ( or parking?) the
gauges (Fuel- Temp- clock -amp?) quit working?
My first thought would be missing a ground on the gauge cluster.
If that were correct- the wipers wouldn't work. Do the wipers function correctly?
Richard
So you have the car ignition on not acc- the gauges work- but when you turn on the headlights ( or parking?) the
gauges (Fuel- Temp- clock -amp?) quit working?
My first thought would be missing a ground on the gauge cluster.
If that were correct- the wipers wouldn't work. Do the wipers function correctly?
Richard
Thread Starter
Burning Brakes
Joined: Jun 2005
Posts: 1,130
Likes: 106
From: laingsburg MI
2020 C3 of the Year Finalist - Modified
To clarify. The gauges work. The lighting for the gauges turn on with the key and turn off when u pull the light switch to on. The speedometer and tach. Lights operate with the head light switch.
Team Owner
Joined: Jan 2006
Posts: 37,637
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From: Crossville TN
You may be missing the ground connection to the gauge cluster gauges. Somehow they are 'finding' ground somewhere else...until you turn on the headlamps. Run a 'dummy' ground wire from known chassis ground point to the chrome edging on the gauge bezel. Then turn ignition ON. Now, turn the headlamps ON. Do you have gauge operation now? If so, install a better [and permanent] ground line to the backside of the gauge bezel.
Le Mans Master
Joined: May 2003
Posts: 8,875
Likes: 3,555
From: Fernandina Beach FL
2023 Restomod of the Year finalist
2020 C3 of the Year Winner - Modified
You may be missing the ground connection to the gauge cluster gauges. Somehow they are 'finding' ground somewhere else...until you turn on the headlamps. Run a 'dummy' ground wire from known chassis ground point to the chrome edging on the gauge bezel. Then turn ignition ON. Now, turn the headlamps ON. Do you have gauge operation now? If so, install a better [and permanent] ground line to the backside of the gauge bezel.
The just lights on the center gauges and NOT the speedo- tach- does point towards a ground- but the center gauge lights are turning on with the ignition?
Where is the +12V coming from?
Possible an aftermarket radio wired incorrectly- but again- the speedo- tach would work in unison with the center gauges.
I'm thinking somebody has rewired the gauge lights incorrectly- or LEDs?
Thread Starter
Burning Brakes
Joined: Jun 2005
Posts: 1,130
Likes: 106
From: laingsburg MI
2020 C3 of the Year Finalist - Modified
No LED lights. I rarely drive the car at night, but I don’t recall there being an issue the last time i did. I have the gauge assembly out to convert the amp gauge to a volt meter. Is it possible that a poor ground is causing this? That after re installation it will work?
Last edited by 73C34me; Aug 14, 2021 at 09:22 AM.
Le Mans Master
Joined: May 2003
Posts: 8,875
Likes: 3,555
From: Fernandina Beach FL
2023 Restomod of the Year finalist
2020 C3 of the Year Winner - Modified
Does the clock work? If so-it's using the same ground.
Odd thing is- without a ground- electricity it will find a path- might be the long one to grandmother's house- but will travel through the light bulb filament ( acts as a resister) to get to a ground.
Now the caveat is- where is the +12v coming from- when you switch the ignition.
I'd pull all the bulbs (gray wire) for illumination out of the cluster. Then ground one of them ( to the little teeth)- and see if they operate correctly.
let us know-
Odd thing is- without a ground- electricity it will find a path- might be the long one to grandmother's house- but will travel through the light bulb filament ( acts as a resister) to get to a ground.
Now the caveat is- where is the +12v coming from- when you switch the ignition.
I'd pull all the bulbs (gray wire) for illumination out of the cluster. Then ground one of them ( to the little teeth)- and see if they operate correctly.
let us know-
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Thread Starter
Burning Brakes
Joined: Jun 2005
Posts: 1,130
Likes: 106
From: laingsburg MI
2020 C3 of the Year Finalist - Modified
I think it was just a crazy grounding backfeed issue with the center instrument gauge cluster out. The center gauge frame was hot , instead grounded. I think when i reinstall i will be good. I hope
Le Mans Master
Joined: May 2003
Posts: 8,875
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From: Fernandina Beach FL
2023 Restomod of the Year finalist
2020 C3 of the Year Winner - Modified
You are getting a switched +12 source touching the metal case. Look over the Fuel- Temp gauges for a broken insulator.- the pink wire is the switched hot source.