headlights only work BRIGHT - Chevelle Tech
Electrical & Wiring Troubleshooting electrical problems.

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post #1 of 7 (permalink) Old Feb 12th, 01, 9:58 AM Thread Starter
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Location: Pittsboro, NC, USA
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For the past week my headlights only work with the brights. I have not had a chance to look at anything yet, but where should I start?
My guess is the switch, but if that's it then how do I verify w/o having a new switch?
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post #2 of 7 (permalink) Old Feb 12th, 01, 10:47 AM
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Start with the basics...

Good grounds for all the headlamps?

Dimmer switch worn out--stuck in the bright position?
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post #3 of 7 (permalink) Old Feb 12th, 01, 1:11 PM
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Sounds dumb, but check the bulbs. If they are old, they may be duds. The dimmer switch is the logical choice, however.
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post #4 of 7 (permalink) Old Feb 12th, 01, 1:45 PM Thread Starter
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One more thing,
I guess I should be more specific.
The gauge dimmer works (rotating the switch) and the parking lights are fine.
The lights stopped working when I parked the car at night (headlights working) and shut off the car and lights. 10 min later, I started the car and there were no lights. -weird.
How could it be the ground if the brights work?
Are there separate bulbs within the headlamps for the low beams and brights?
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post #5 of 7 (permalink) Old Feb 12th, 01, 2:27 PM
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I had the same problem with my low beam passenger side light. it would work on high but when just normally on it would not work. someone told me it was only one bulb so i just turned the brights on and disconnected the brights lights. i would be interested to know what is happening.
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post #6 of 7 (permalink) Old Feb 12th, 01, 11:34 PM
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Did you ever notice you house light bulbs never burn out while they are on, only after you shut them off or just turn them on. Headlamps can do the same thing. There are 2 filaments inside the sealed unit, one for normal and one for brights. Living in a city sometimes you don't notice when one of your lights are out, it is only when they all fail it becomes apparent. I had a 62 Impala and did exactly that. Turned on the lights one night and couldn't see. When I checked both low beams were out and 3 of the hi beams. After installing 4 new headlamps all was fine.


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post #7 of 7 (permalink) Old Feb 14th, 01, 6:20 AM
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I checked my wiring diagrams for my '69 last night. Your's may be different, but I'll give you my info in case they're the same or similar.

Wiring to high and low beam lamps come from the dash, independently, via the forward lighting harness. Both come from the hi/low switch. The color of the low beam power wire is Teal (#16). Since none of your low beam lamps work, I would suspect that there could be a loose or broken wire somewhere between the switch and the first lamp. It could be at the lamp, at the bulkhead connector or at the switch. It is at the switch where the power for both low and high beam lamps have a common source (headlight switch). Since your high beam lamps work, grounding should not be the problem. Both high and low lamps share a ground.

Of cource another possible cause could be the switch itself.

To help in your troubleshooting, turn on your lights and check the voltage at the first light. If no voltage there, check the output of the switch. That should tell you if the problem is with the switch or with the wiring.

Let us know what you find.

Randy Hammett
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