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Having issues with dash lights. Lights on dash not working, except for high beams light. They did not work most of the time when I purchased car. Assumed it was the main dash switch. Posted thread about this and was directed to a thread by Greg that talked about-grounds and switching dash lights to two wire with common grounds . While I was doing that I switched them over to 194 LED’s.
Replaced main dash light switch. Hooked up to ground by drivers side door and was excited for the results, Only light that will work is High Beam light. Out of all the gauges that is the only one, why? Now the brake and rear running lights are now not working either.
Checked and replaced fuses and still not working. Any help is greatly appreciated.
The car is a C3, 1973 Coupe 350 [L-48)
Last edited by RobMc1963$; Jan 31, 2021 at 11:48 PM.
Reason: More information
Not sure what year you are dealing with, but on my 69 there is a ground wire and stud on the back of the speedometer, and the tach, and also a double black that grounds on a terminal mounted to the underside of the ash tray. These are in addition to the one you mentioned in front of the driver side door.
As far as the brake and tail lights, did that just start to happen? Sounds like something happened with replacing the head light switch which it sounds like you did. Also, as dumb as it sounds, make sure you don’t have the dash lights off by having the headlight switch turned all the way to the right.
Last edited by 69ttop502; Jan 31, 2021 at 09:30 PM.
2025 c3 ('74-'82) of the Year Finalist - Unmodified
2019 C3 of Year Finalist (appearance mods)
The headlight switch needs a separate ground, do you have #7 installed?
The tail lamp fuse sends power to the instrument light fuse, are they both good?
If the instrument fuse blows only the dash lights will go out.
If the tail light fuse blows both the instrument lights and the tail lights will be out.
Also is the green wire at the headlight switch plugged in properly?
Make sure the multi pin large connector that mates with the head light/vacuum switch is correctly plugged in. I didn’t have mine right and lost my dash lights.
Yes to new switch ground installed. Both fuses un-blown.
Did you test the fuses or just inspect them?
Old fuses can often pass a simple visual inspection but not pass current as sometimes the caps disconnect from the metal strip.
Be sure you verify your fuses are good using a volt meter by checking for voltage at both caps of the installed fuse.
There have been similar light issues from other Forum Members that turned out to be the large connector on the engines idle firewall that connects to the fuse box, wiring harness. If you everything checks out ok at the Harmonica Connector, take a look at the connector.
The reason the headlight "high beam" lights up- is it's on a separate circuit and fed power from the dimmer switch.
LEDs are one way devices- often time the aftermarket bulb holders use white as ground and black as +12- that could be your problem.
Here's a simple hack-
Get a 9V battery and one of the connectors- you can get one out of a old trashed electronic piece- radio- even an old smoke detector ( that should be replaced every 10 years anyway)
If you have a spare bulb holder and LED- try it out with a 9V battery- if not you can test the car -
Disconnect your car battery-
Take the leads and touch the instrument lamp fuse (try both sides) with the red and the black to ground. Then swap the leads around. The LEDs will work fine off a 9V battery.
If it lights up with the 9V battery leads swap around - there's your problem.
Did you test the fuses or just inspect them?
Old fuses can often pass a simple visual inspection but not pass current as sometimes the caps disconnect from the metal strip.
Be sure you verify your fuses are good using a volt meter by checking for voltage at both caps of the installed fuse.
I visually inspected only. I am getting new ones today to make sure.
The reason the headlight "high beam" lights up- is it's on a separate circuit and fed power from the dimmer switch.
LEDs are one way devices- often time the aftermarket bulb holders use white as ground and black as +12- that could be your problem.
Here's a simple hack-
Get a 9V battery and one of the connectors- you can get one out of a old trashed electronic piece- radio- even an old smoke detector ( that should be replaced every 10 years anyway)
If you have a spare bulb holder and LED- try it out with a 9V battery- if not you can test the car -
Disconnect your car battery-
Take the leads and touch the instrument lamp fuse (try both sides) with the red and the black to ground. Then swap the leads around. The LEDs will work fine off a 9V battery.
If it lights up with the 9V battery leads swap around - there's your problem.
Let us know what you find-
Richard
But they must be hooked up correctly since the High Beam light is working with the same setup.
The reason the headlight "high beam" lights up- is it's on a separate circuit and fed power from the dimmer switch.
LEDs are one way devices- often time the aftermarket bulb holders use white as ground and black as +12- that could be your problem.
Here's a simple hack-
Get a 9V battery and one of the connectors- you can get one out of a old trashed electronic piece- radio- even an old smoke detector ( that should be replaced every 10 years anyway)
If you have a spare bulb holder and LED- try it out with a 9V battery- if not you can test the car -
Disconnect your car battery-
Take the leads and touch the instrument lamp fuse (try both sides) with the red and the black to ground. Then swap the leads around. The LEDs will work fine off a 9V battery.
If it lights up with the 9V battery leads swap around - there's your problem.
Let us know what you find-
Richard
exactly why I suggested troubleshooting with bulbs first before led/diodes.
Last edited by augiedoggy; Feb 1, 2021 at 01:16 PM.
The headlight switch needs a separate ground, do you have #7 installed?
The tail lamp fuse sends power to the instrument light fuse, are they both good?
If the instrument fuse blows only the dash lights will go out.
If the tail light fuse blows both the instrument lights and the tail lights will be out.
Also is the green wire at the headlight switch plugged in properly?
Every persons nightmare, Electrical (Dash)
