Headlight on, gauges stop working
Thread Starter
8th Gear
Joined: Dec 2023
Posts: 8
Likes: 0
Headlight on, gauges stop working
Hello,
I have a 1978 C3 base model, my gauges in the center console work just fine when the headlights are off. However, when I turn the headlights on, and only when the headlights are on, my gauges seems to lose power and get whacky. My battery gauge drops to 8V, fuel gauge drops but not to E, temperature gauge red lines, and the oil pressure drops but not to zero. The battery has been on the charger all night and shows fully charged, the car starts just fine. I have no idea what would be causing this problem.
I should also mention that I had the center console, speedo and tachometer gauges out to replace the light bulbs.
Any suggestions would be appreciated.
Thanks,
I have a 1978 C3 base model, my gauges in the center console work just fine when the headlights are off. However, when I turn the headlights on, and only when the headlights are on, my gauges seems to lose power and get whacky. My battery gauge drops to 8V, fuel gauge drops but not to E, temperature gauge red lines, and the oil pressure drops but not to zero. The battery has been on the charger all night and shows fully charged, the car starts just fine. I have no idea what would be causing this problem.
I should also mention that I had the center console, speedo and tachometer gauges out to replace the light bulbs.
Any suggestions would be appreciated.
Thanks,
Last edited by luke78; Jan 21, 2024 at 04:10 PM.
Thread Starter
8th Gear
Joined: Dec 2023
Posts: 8
Likes: 0
Hello,
I have a 1978 C3 base model, my gauges in the center console work just fine when the headlights are off. However, when I turn the headlights on, and only when the headlights are on, my gauges seems to lose power and get whacky. My battery gauge drops to 8V, fuel gauge drops but not to E, temperature gauge red lines, and the oil pressure drops but not to zero. The battery has been on the charger all night and shows fully charged, the car starts just fine. I have no idea what would be causing this problem.
I should also mention that I had the center console, speedo and tachometer gauges out to replace the light bulbs.
Any suggestions would be appreciated.
Thanks,
I have a 1978 C3 base model, my gauges in the center console work just fine when the headlights are off. However, when I turn the headlights on, and only when the headlights are on, my gauges seems to lose power and get whacky. My battery gauge drops to 8V, fuel gauge drops but not to E, temperature gauge red lines, and the oil pressure drops but not to zero. The battery has been on the charger all night and shows fully charged, the car starts just fine. I have no idea what would be causing this problem.
I should also mention that I had the center console, speedo and tachometer gauges out to replace the light bulbs.
Any suggestions would be appreciated.
Thanks,
Melting Slicks
Joined: Jun 2014
Posts: 2,236
Likes: 498
From: NJ
Check for a missing or loose ground wire.
Is my vette stock?? HAHA
Joined: Oct 2015
Posts: 20,212
Likes: 9,350
From: Im not allowed to tell you
2020 C3 of the Year Finalist - Modified
2020 Corvette of the Year Finalist (performance mods)
2019 C3 of Year Winner (performance mods)
2016 C3 of Year Finalist
Either you have a missing ground on your console or its cracked and you have to add one....the dash lights are chasing a ground through your gauges for a path...
You could disconnect all the dash bulbs one at a time while watch the gauges on the off chance its only one light socket...doubt it
You could disconnect all the dash bulbs one at a time while watch the gauges on the off chance its only one light socket...doubt it
Is my vette stock?? HAHA
Joined: Oct 2015
Posts: 20,212
Likes: 9,350
From: Im not allowed to tell you
2020 C3 of the Year Finalist - Modified
2020 Corvette of the Year Finalist (performance mods)
2019 C3 of Year Winner (performance mods)
2016 C3 of Year Finalist
On older models there is a metal tab the grounds the switch to the dash housing for the dimmer system...good catch
Thread Starter
8th Gear
Joined: Dec 2023
Posts: 8
Likes: 0
Okay, so I found a solution and as we all suspected it was a ground issue.
I have the center console apart and removed the cigarette lighter, well the ground for the cigarette lighter just happened to touch metal and my gauges and lights started working normally. :-)
I'm ordering a new light switch Monday because the interior dome lights only come on when the switch is in the perfect position, so there's obviously an issue there. When I replace the switch if I still have issues with the gauges and lights then I'll just run a new ground wire from the cigarette lighter to the body to reestablish a ground connection.
Thank you all for taking time to read and reply to my issue.
Have a great day.
I have the center console apart and removed the cigarette lighter, well the ground for the cigarette lighter just happened to touch metal and my gauges and lights started working normally. :-)
I'm ordering a new light switch Monday because the interior dome lights only come on when the switch is in the perfect position, so there's obviously an issue there. When I replace the switch if I still have issues with the gauges and lights then I'll just run a new ground wire from the cigarette lighter to the body to reestablish a ground connection.
Thank you all for taking time to read and reply to my issue.
Have a great day.
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Thread Starter
8th Gear
Joined: Dec 2023
Posts: 8
Likes: 0
If anyone needs it, here's a link to the Electrical Troubleshooting Manual for a 1978: https://drive.google.com/file/d/10F2...ew?usp=sharing
Le Mans Master
Joined: Apr 2008
Posts: 9,434
Likes: 239
From: Powassan ON
Question, as it’s related to the topic at hand.
Is the lighter under constant hot? ie: powered up all the time, regardless of key position
I disconnected mine as it was a power draw and potential for fire. Never used or needed it anyway.
I read here, somewhere, years ago a lighter is a good place for a car fire to start, due to the constant power.
Is the lighter under constant hot? ie: powered up all the time, regardless of key position
I disconnected mine as it was a power draw and potential for fire. Never used or needed it anyway.
I read here, somewhere, years ago a lighter is a good place for a car fire to start, due to the constant power.
Le Mans Master
Joined: Aug 2006
Posts: 7,426
Likes: 1,559
From: mount holly NC
2025 c3 ('74-'82) of the Year Finalist - Unmodified
2019 C3 of Year Finalist (appearance mods)
1-23
Thanks for the follow-up answer and the link for the troubleshooting guide.
Your suggestion made me order one for my '74.
Pete.
Your suggestion made me order one for my '74.
Pete.
If anyone needs it, here's a link to the Electrical Troubleshooting Manual for a 1978: https://drive.google.com/file/d/10F2...ew?usp=sharing