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Independent Headlight Vacuum Control.
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From: Connecticut
its more of a fabrication job, unless C3s had a factory option for it.. alot of 80s cars did (push button hvac control instead of slider)
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Melting Slicks
Joined: Jul 2004
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From: Long Island New York
My headlights come up when I put the headlight switch in the parking lights position. They do not on turn on though until I pull the switch out the rest of the way. Is it the headlight switch that's bad or is it the relays, anyone know? Sorry, didn't mean to hijack your thread.
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From: Springfield MO
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My headlights come up when I put the headlight switch in the parking lights position. They do not on turn on though until I pull the switch out the rest of the way. Is it the headlight switch that's bad or is it the relays, anyone know? Sorry, didn't mean to hijack your thread.
Thread Starter
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Joined: Aug 2006
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From: Columbia Missouri
My headlights come up when I put the headlight switch in the parking lights position. They do not on turn on though until I pull the switch out the rest of the way. Is it the headlight switch that's bad or is it the relays, anyone know? Sorry, didn't mean to hijack your thread.
Actually that's supposed to happen. Say you lock your headlights in the up position and move the switch to the park light position, all lights should come on with the exception of the headlights. I think even the taillights come on.
This same operation applies when the vacuum is switched and the headlight assemblies rise even though power to the headlights is not switched on.
This would not be bad, I just want the headlights up so I can use my halos and nothing else when the daylight starts to fail and the halos look best. Once it gets too dark I can then switch off the halos and turn the headlights and all related lights on.
Melting Slicks
Joined: Mar 2006
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From: Connecticut
My headlights come up when I put the headlight switch in the parking lights position. They do not on turn on though until I pull the switch out the rest of the way. Is it the headlight switch that's bad or is it the relays, anyone know? Sorry, didn't mean to hijack your thread.
It sounds like the switch is starting to wear out and it's supplying vacuum too early.
The vacuum ports should only be open when the switch is pulled out fully.
If you look at this pic it may give you a better idea of how the vacuum is synchronized with the electric on the switch.
Last edited by Bob Onit; Sep 28, 2007 at 09:49 AM.
Thread Starter
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From: Columbia Missouri
Bob - All three of my '77 Vettes did the same thing. When the headlight switch is moved to the parking light position the headlight assemblies raise up but the headlights don't illuminate.
Melting Slicks
Joined: Nov 2001
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From: Eastern US XX
My 69 Vacuum system works perfectly, but doesn't behave that way. When I have the parking lights on, headlights are down and off, but all other lights come on.
Melting Slicks
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From: Connecticut
Melting Slicks
Joined: Nov 2001
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From: Eastern US XX
I don't believe the headlights should come up unless they are on or the vacuum override "switch" under the steering column is pulled down.
The fact that the switch is the same for 68-77, I suspect that "all three" of Matt's '77s had failing switches!
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Joined: Jan 2006
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From: Wilmington DE, Drive it like you stole it, 68 327 4 speed coupe
Same on the 68 first pull parking lamps lights down, second pull lights up and on, all my vacuum stuff is fully funtional, if not a little sleepy on the left
That's not normal.