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For the last few weeks I’ve been having the problem of my brake lights not working when my headlights are turned on. As you guys know when the headlights are on the dash lights turn on. A few weeks ago the dash lights also stopped working. I replaced the light switch,(fixed nothing) and the wiring connector, (because it was cracked and burned.) I’m returning the new light switch because the **** wouldn’t stay in. I’ve made sure the ground for the tail lights in good. Along with headlight grounds, and dash ground. I’ve looked at the wiring and I haven’t seen anything wrong new my inexperienced eye. Im wondering if anyone can help me. I’ve been banging my head on the wall after school for that last few days with no results. Thanks. I’ll try any suggestions.
Do you have a wiring diagram? Are you chasing the circuit?
Yes. I’ve been fallowing the wires for the dash and brakes. I’ve been using a wilcox corvette diagram.
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Yes the ground plate is attached but only where the switch is, not to the speedo. The speedo only has one screw. I got the car like that. Could that be the problem? It’s never been attached to the speedo since I’ve been digging around with it and they used to work.
Yes. I’ve been fallowing the wires for the dash and brakes. I’ve been using a wilcox corvette diagram.
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Yes the ground plate is attached but only where the switch is, not to the speedo. The speedo only has one screw. I got the car like that. Could that be the problem? It’s never been attached to the speedo since I’ve been digging around with it and they used to work.
Yes the ground plate attaches to the speedo housing otherwise the switch is not grounded.
Is the black ground wire attached to the door jam?
Is the little LPS fuse good?
Yes, ground wire is attached, yes I have the #7. the speedo screws have been taken 25 years ago so it hasn't been attached. Could that be it? The LPS fuse is the only one I haven't replaced. Thanks for the diagrams.
Last edited by CarterDawson; Nov 19, 2022 at 04:10 PM.
The dark green wire on the switch should have power when the switch is pulled. The voltage should change when you turn the ****. The INST LPS fuse should have the same voltage as the dark green wire.
Like bruiser diagram shows,
You will only see voltage at the 5 AMP INST/LPS fuse when you pull the **** to either Head or Park position.
The Tail 20 AMP fuse powers that portion of the Headlight Switch.
Now about the Ground Strap and missing screw,
When you turn the **** full CCW a set of external switch contacts close sending a ground path to the Courtesy light circuit.
If "Both" doors are closed and you want your interior lights to come on, this will be the ONLY ground path available to the Courtesy light bulbs...
If you can find the missing screw great, or you could make up a jumper wire with an eyelet at each end and use the straps eyelet through bolting a screw and nut and then land the other end of your ground jumper wire to a good known chassis ground.
Here is another diagram showing the Headlight Switch ground path to Courtesy light circuit.
Looking at your new Headlight Switch connector pigtail, I believe it is now the Yellow Wire...
Last edited by bmotojoe; Nov 19, 2022 at 07:22 AM.
I went out today and attached the ground plate, and the speedo ground, and tach ground. Nothing. The headlights still turn on but that's it. No dash lights. The bulbs are good. I attached a jumper cable to the negative terminal on the battery and the other end to the ground plate. Still nothing. I know that there's a ground strap under the car Infront of the drives side door. And it's torn from the other end. I don't know where it goes to. could that be contributing to the problem?
All plugged in. Ground plate attached. The only screw I could fit in the hole is tapered at the head. I don’t think there’s anything wrong with that right? Turned on, no lights.
It could be broken out of the box. Have you tried twisting the ****? While you have access, can you check for voltage entering and leaving the dash light dimmer circuit?
It looks like you can see the resistor element in your first image of your latest post.
I just got done chasing around the same problems with my '77. I bought the Doc Rebuild oOSOEZ wiring chart and it was the best investment that I have ever made with my Corvette.
Aside from changing all of the fuses, did you multi-meter both sides at the fuse panel? This is also helpful.
It could be broken out of the box. Have you tried twisting the ****? While you have access, can you check for voltage entering and leaving the dash light dimmer circuit?
It looks like you can see the resistor element in your first image of your latest post.
Yes, the one in the photo is brand new. I put the old one in too and had the same results. Yes, I turned the ****. I went and tested the contacts on both sides of all the fuses and the fuse bord and I get voltage. I don't know how to test the voltage on the switch. Before I replaced the fuses, I noticed the old ones had gotten wet. I'm wondering if I should pull the fuse box and see if the wire contacts are still good where the wires go in to the fuse box.
I just got done chasing around the same problems with my '77. I bought the Doc Rebuild oOSOEZ wiring chart and it was the best investment that I have ever made with my Corvette.
Aside from changing all of the fuses, did you multi-meter both sides at the fuse panel? This is also helpful.
I did check all the fuse contacts. They all pass thru the fuse. I dint check the box as a whole, not sure how. Did you also have the problem with the headlights turning on and having no brake lights, intill you turn the lights off? All my grounds are good so that's not the problem. do you think that where the wires go into the fuse box from the light switch may be corroded?
Last edited by CarterDawson; Nov 19, 2022 at 04:09 PM.
im newer to the forum, is there a way to reply to you guys without have to quote you guys. thanks
You can just type a quick reply. Quoting is helpful (if you delete the photo), as it lets us know what question is being asked and answered.
You can even quote from different sources, once you understand the format.
Originally Posted by Abraham Lincoln
Not everything you read on the internet is true.
Originally Posted by CarterDawson
Yes, the one in the photo is brand new. I put the old one in too and had the same results. Yes, I turned the ****. I went and tested the contacts on both sides of all the fuses and the fuse bord and I get voltage. I don't know how to test the voltage on the switch. Before I replaced the fuses, I noticed the old ones had gotten wet. I'm wondering if I should pull the fuse box and see if the wire contacts are still good where the wires go in to the fuse box.
With the diagrams others have posted (another one is at the link below), perhaps you can pull the headlight connector off, and check for voltage going into your switch. With a diagram of the switch, you should be able to see which pins are the pass-thru for the (dimmable) instrument lighting. You can check that the resistance changes when you turn the ****, and that at one position there is nearly zero resistance.
For checking voltage on the outbound side of the switch, a wire-insulation piercing test light is helpful, or you can get needle or wire piercing probes for your multimeter.
Dash lights quit working 76 vette
