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72' Headlamp Switch - Bright Light Indicator Not Working
1972 L48
I was having some lighting issues and I replaced the headlamp switch. Before I replaced the switch my instrument backlighting was not working and the courtesy lights would not come on when turning the headlamp switch. However, the turn signal indicators, break indicator, and bright light indicator lights all worked. Now that I have replaced the headlamp switch, courtesy lighting now works, turn signal indicators and break indicator lights work, but now the bright light indicator no longer works. Additionally, the instrument backlighting still does not work. I replaced all bulbs with new ones that I bench tested before installing, thus I am reasonably sure this is not a bulb issue. I have checked all the fuses, no issues there. I verified the ground wirers to both the speedometer and the tach were clean and connected.
I think this needs to be assessed as two problems. First the bright light indicator light; it worked before and now it does not. Second, the instrument backlighting still doesn't not work regardless of replacing out the headlamp switch. I feel like this is a ground issue, but I am not sure and was hoping to get other thoughts.
Maybe an obvious question, you turned the headlight switch counterclockwise to check the dashlights?
Do the high beams come on when you step on the floor switch?
I should have clarified in my original post, thank you for the clarifying questions.
Yes, the low beam and high beam headlights come on when pressing the floorboard button switch. The dashlights do not come on not matter what I do with the headlamp switch.
2020 Corvette of the Year Finalist (performance mods)
2019 C3 of Year Winner (performance mods)
2016 C3 of Year Finalist
If they do not illuminate with the rheostat there is a seperate ground that goes from the switch to the tach. That could be one issue. If your dash lights do not work at all you need to see if there is power to the wqoring when the light switch is pulled. You will only get power to the fuses when the light switch is pulled. I had a wiring issue inside the fuse block that didnt get power to the dash bulbs. Also If the bulb is not illuminating for the high beams check to see if the bulb didnt fall out or if the socket just didnt pop out of the location and is jsut swinging back there. Again you need to trace power to see where it is and where it isnt so we arent just guessing
Where is the ground connection on the switch that runs to the tach? There were two separate ground wires that attached to the back of the speedometer and tach. But I did not see a separate ground connection on the tach or any wires running directly from the lamp switch to the tach.
Good thoughts on the potential wiring issue inside the fuse block, I will check that out.
On your fuse panel, the dash lights (grey wire) comes right off the lower fuse, that fuse gets power (dk green) from the light switch on the inside (towards the middle of the fuse panel) when the lights are turned on. Check and make sure there is power going to and through that fuse when the lights are turned on.
The hi-beam indicator gets it's power from the floor switch which is the same output as what goes to the headlight so if they are turning on (hi) then there should be power to that bulb
The drivers dash is grounded via the two tabs on the tach and speedo housings
You could try a jumper or check for continuity to ground
Are you positive that the large plastic wiring connector is attached Correctly to the headlight switch? I tried to connect mine without removing the dash pad completely, guess what … No Dash Lights. I didn’t align the plug correctly. There have been a number of posts on bad fuses that look good, as well as corrosion on the fuse metal holders. Checking for 12 volts can be done at the center gauge cluster easily, by testing any illuminator bulb. Good Hunting.
I had the entire dashboard pulled. Interesting that you mentioned the plastic connector wire, I wondered the same thing. I am going to pull the dash pad and driver-side dash cluster again and check that again. I am familiar with all the grounds, but where does the instrument backlighting get their power from directly, this question applies to both the speedo and tach, but also the center gauge cluster and shift console?
The positive 12 volts that goes to all gauge light has to originate at the head light switch
(rheostat with wire winding), that is how you are able to dim the bulbs. Check to see if you have 12 volts at any bulb (use a temporary ground). If there is no voltage and you have tried all the other suggestions, make sure that the metal “grounding arm” from the head light switch is touching the speedo case.
I seem to remember a thread on here a while back about a brand new headlight switch that was less than ideal quality and the contact wasn’t making contact all the way around the rheostat. The owner had to physically rework the switch a bit to be functional. May be your issue?
As far as the high beam light, is it possible it popped out of its socket during dash reinstall and is just hanging back there, but still working?
I seem to remember a thread on here a while back about a brand new headlight switch that was less than ideal quality and the contact wasn’t making contact all the way around the rheostat. The owner had to physically rework the switch a bit to be functional. May be your issue?
As far as the high beam light, is it possible it popped out of its socket during dash reinstall and is just hanging back there, but still working?
If they do not illuminate with the rheostat there is a seperate ground that goes from the switch to the tach. That could be one issue. If your dash lights do not work at all you need to see if there is power to the wqoring when the light switch is pulled. You will only get power to the fuses when the light switch is pulled. I had a wiring issue inside the fuse block that didnt get power to the dash bulbs. Also If the bulb is not illuminating for the high beams check to see if the bulb didnt fall out or if the socket just didnt pop out of the location and is jsut swinging back there. Again you need to trace power to see where it is and where it isnt so we arent just guessing
I had the opportunity to pull the dash again. No Brights blue light indicator, and no instrument lighting. Brake light and signal lights all work. Cener console, the headlamp indicator light works when headlights come on, but no gauge lighting. Even the clock works...go figure. So here is the breakdown.
1. All new bulbs, all bench tested working before I installed.
2. New headlamp switch.
3. All grounds verified connected (metal piece from switch to speedo mount, both grounds to the back of speedo and tach, ground from harness to body frame on driver's side.
4. All fuses replaced with new ones.
5. Headlights and brights work.
6. Courtesy lights work when doors are open, and when headlamp switch is turned.
At this point I think your idea of the power to wiring from the fuse box to the switch might be the issue, or maybe a bad headlamp switch. Could you provide some details about how you troubleshot your fuse box and fixed the issue? How did you test? What specific color wire was the issue? Where did the wire originate and terminate?
2020 Corvette of the Year Finalist (performance mods)
2019 C3 of Year Winner (performance mods)
2016 C3 of Year Finalist
My issue was no power coming out after the fuses for my dash and tail lights. I used a multimtete and started at the light bulbs and kept searching for power to the switch, to the fuses and back to the switch.
In you situation did you say you did have high beams but no indicator? I would make sure your tach ground is good with the meter, then check a known good power sorce to compare your bulb power to. Check there, the switch, and trace it on a diagram. When i had my issue i pulled the fuse box off the firewall to check the back of it.
A wiring diagram will help to trace the power through the highbeam switch to see whats going on thete. I do remember they can cause weird issues
My issue was no power coming out after the fuses for my dash and tail lights. I used a multimtete and started at the light bulbs and kept searching for power to the switch, to the fuses and back to the switch.
In you situation did you say you did have high beams but no indicator? I would make sure your tach ground is good with the meter, then check a known good power sorce to compare your bulb power to. Check there, the switch, and trace it on a diagram. When i had my issue i pulled the fuse box off the firewall to check the back of it.
A wiring diagram will help to trace the power through the highbeam switch to see whats going on thete. I do remember they can cause weird issues
72' Headlamp Switch - Bright Light Indicator Not Working
