78 C3 light switch issues
Thread Starter
Burning Brakes
Joined: Apr 2008
Posts: 825
Likes: 40
From: Glasgow, Scotland
78 C3 light switch issues
Hey there, my 78 corvette light switch stopped working, so got a new one, but still no working, if i take a wire from the live feed into the light switch plug and touch on spades, i can get the lights working, so something to do with switch, does the switch need to be earthed?, its body??
anyone with any ideas?
thanks
anyone with any ideas?
thanks
Burning Brakes
Joined: May 2013
Posts: 789
Likes: 129
From: Los Banos CA
Do you have a wiring diagram? It's been several years since I removed my light switch, but I don't remember the switch body needing to be grounded. Here's what I would do, in this order (I'm assuming wire colors are similar to my 79):
1- There should be a black wire in the switch harness. Try grounding the black wire connector to a good ground (or the battery negative cable) and see if that changes anything.
2 - You should have a red wire that has voltage all of the time. If you touch a live feed on this connection, and the lights work, then you're not getting voltage TO the switch. Check for a bad fusible link near the starter (my wiring diagram shows that the wire should be red with a white stripe running down to the starter).
3 - The wire color for the 'lights on' wire is yellow - if you touch a live feed to the yellow wire and the lights work, then the switch is probably bad (provided that step 1 and 2 didn't change anything). This yellow wire runs to the beam select switch, then to the headlights.
If you're not getting any dome light/taillights/side marker lights, my guess would be #1 or #2 will point to the problem.
Hope this helps.
1- There should be a black wire in the switch harness. Try grounding the black wire connector to a good ground (or the battery negative cable) and see if that changes anything.
2 - You should have a red wire that has voltage all of the time. If you touch a live feed on this connection, and the lights work, then you're not getting voltage TO the switch. Check for a bad fusible link near the starter (my wiring diagram shows that the wire should be red with a white stripe running down to the starter).
3 - The wire color for the 'lights on' wire is yellow - if you touch a live feed to the yellow wire and the lights work, then the switch is probably bad (provided that step 1 and 2 didn't change anything). This yellow wire runs to the beam select switch, then to the headlights.
If you're not getting any dome light/taillights/side marker lights, my guess would be #1 or #2 will point to the problem.
Hope this helps.
Thread Starter
Burning Brakes
Joined: Apr 2008
Posts: 825
Likes: 40
From: Glasgow, Scotland
Do you have a wiring diagram? It's been several years since I removed my light switch, but I don't remember the switch body needing to be grounded. Here's what I would do, in this order (I'm assuming wire colors are similar to my 79):
1- There should be a black wire in the switch harness. Try grounding the black wire connector to a good ground (or the battery negative cable) and see if that changes anything.
2 - You should have a red wire that has voltage all of the time. If you touch a live feed on this connection, and the lights work, then you're not getting voltage TO the switch. Check for a bad fusible link near the starter (my wiring diagram shows that the wire should be red with a white stripe running down to the starter).
3 - The wire color for the 'lights on' wire is yellow - if you touch a live feed to the yellow wire and the lights work, then the switch is probably bad (provided that step 1 and 2 didn't change anything). This yellow wire runs to the beam select switch, then to the headlights.
If you're not getting any dome light/taillights/side marker lights, my guess would be #1 or #2 will point to the problem.
Hope this helps.
1- There should be a black wire in the switch harness. Try grounding the black wire connector to a good ground (or the battery negative cable) and see if that changes anything.
2 - You should have a red wire that has voltage all of the time. If you touch a live feed on this connection, and the lights work, then you're not getting voltage TO the switch. Check for a bad fusible link near the starter (my wiring diagram shows that the wire should be red with a white stripe running down to the starter).
3 - The wire color for the 'lights on' wire is yellow - if you touch a live feed to the yellow wire and the lights work, then the switch is probably bad (provided that step 1 and 2 didn't change anything). This yellow wire runs to the beam select switch, then to the headlights.
If you're not getting any dome light/taillights/side marker lights, my guess would be #1 or #2 will point to the problem.
Hope this helps.
Burning Brakes
Joined: May 2013
Posts: 789
Likes: 129
From: Los Banos CA
Here's a video that covers bench testing the switch - it might help also.
I'm not 100% certain, but I think the red wire might only be used to source the headlights (unfused), and the orange wire might supply voltage for the taillights/side markers. Check for voltage on both the red and orange wires. Good luck!
I'm not 100% certain, but I think the red wire might only be used to source the headlights (unfused), and the orange wire might supply voltage for the taillights/side markers. Check for voltage on both the red and orange wires. Good luck!
Thread Starter
Burning Brakes
Joined: Apr 2008
Posts: 825
Likes: 40
From: Glasgow, Scotland
Here's a video that covers bench testing the switch - it might help also.
https://www.youtube.com/watch?v=ryuwnYO9GUw
I'm not 100% certain, but I think the red wire might only be used to source the headlights (unfused), and the orange wire might supply voltage for the taillights/side markers. Check for voltage on both the red and orange wires. Good luck!
https://www.youtube.com/watch?v=ryuwnYO9GUw
I'm not 100% certain, but I think the red wire might only be used to source the headlights (unfused), and the orange wire might supply voltage for the taillights/side markers. Check for voltage on both the red and orange wires. Good luck!
Racer
Joined: Jan 2017
Posts: 271
Likes: 120
From: Rock Hill South Carolina
To answer your ground question: There is a ground strap that’s supposed to run from the speedo housing to the headlight switch mount.
i assume you have one since you used to have headlights, but sometime it doesn’t hiurt to point out the obvious 🙂.
i assume you have one since you used to have headlights, but sometime it doesn’t hiurt to point out the obvious 🙂.
Thread Starter
Burning Brakes
Joined: Apr 2008
Posts: 825
Likes: 40
From: Glasgow, Scotland
thank you for that info, my dash broad is gone, so didnt know weather it should be or not earthed, will try adding a earth strap to light housing, cheers
Melting Slicks
Joined: May 2015
Posts: 2,365
Likes: 428
From: Cape Girardeau Missouri
There's no ground strap to the headlamp switch for 78+
There is a ground (black) wire leading to the switch but it's used only for turning on the courtesy lights. All other switch functions work without the ground.
There is a ground (black) wire leading to the switch but it's used only for turning on the courtesy lights. All other switch functions work without the ground.
Corvette Stories
The Best of Corvette for Corvette Enthusiasts
Top 10 Most Expensive Corvettes Ever Sold on Bring A Trailer
Brett Foote
10 Things Every Corvette Owner Needs (2026 Edition)
Michael S. Palmer
8 Most "Only Corvette Owners Understand" Quirks and Problems
Pouria Savadkouei
10 Reasons the C6 Z06 is Still A Performance Benchmark After 20 Years
Joe Kucinski
How Much Horsepower Every Corvette Engine "LOST" in 1972
Joe Kucinski
Top 10 DOs and DON'Ts for Protecting Your Convertible Top!
Michael S. Palmer
Top 10 Most Explosive Corvettes Ever Made: Power-to-Weight Ratio Ranked!
Joe Kucinski
150 hp to 1,250 hp: Every Corvette Generation Compared by the Specs That Matter
Joe Kucinski
8 Coolest Corvette Pace Cars (and Replicas) of All Time
Verdad Gallardo
Le Mans Master
Joined: Sep 2002
Posts: 5,236
Likes: 898
From: Myrtle Beach SC
Headlamps are vacuumed operated...meaning the headlamps could be on but fail to rotate up, which suggests the vacuum system is not working. You say the lights are on and say they are not...assuming you mean headlamps vs. dome light vs footwell lighting. So clarify.