Topic: headlight relays
in Forum: C3 Body
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I have a very common problem with my headlights not comming up together. After determining that the relays were bad I replaced both. headlight open and close fine just not together. I switched the relays and had the same problem just opposite sides so it must be that one relay moves slower than the other. While sitting quietly trying the Vulcan Mind Meld with my Vette (I do that alot trying to find answers) I asked why there were 2 relays. I tried teeing off of one relay to both actuators and capping the tank supply to the other and presto headlights work perfectly.
78silver 2008-09-01 09:36:31
Does anyone know why two relays are used to accomplish 1 task?
I can't think of another way to repair them other than buying more relays and hope they work at the same speed.
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Cramerton, NC - USA
Joined: 8/22/2006
Posts: 1094
Vette(s): black 1982 coupe slate gray interior, 350 crossfire, 1985 fuel pump, Steeroids R&P conversion
Some members in the past have indicated that they used only one relay for both lights by "T"ing off the lines. I dont know of any detrimental effect of doing that. One reason I can think of for having two is in case there is a failure of one, you will have the other light working to get home at night until you can get it repaired, a fail-safe if you will. If you must have both lights open at precisely the same instant, you may try restricting the vacuum flow on the fast light very slightly until it matches the speed of the slower light. Dont know if that will work or not but it would sure be cheaper and easier than buying new relays and hoping for the right speed.
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Anaheim Hills, CA - USA
Joined: 8/25/2008
Posts: 42
Vette(s): 1980 Coupe Red 350/Auto - 1968 Coupe Black 427/390/4sp - 08 Coupe Black 6.2 Auto(wifes C6)
On my 80 they come up at the same time and on my 68 the right one is about a 1/2 second slower than the left.
Lifetime Member[QUOTE=mkapp7879]The lights don't come up together on ANY of my Vettes.[/QUOTE]
Agree with Mike, the headlights on my Pacer go Klunk then Klunk 
One at a time.
One at a time.MARK
LIFETIME MEMBER #117 
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"Keep up the Pace"
As long as they are close, it's not a problem.
The difference can be caused by a vacuum leak. The leak can be the seals on the light vacuum actuators. Those are replaceable.
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Mounds View, MN - USA
Joined: 5/24/2007
Posts: 1031
Vette(s): 70 LT1 coupe, 69 350 HP coupe, 69 390HP 427 coupe, 71 LS5 convert, 85 coupe, 93 coupe
I hate to interrupt all the "Klunk"ing, but I wanted to mention that 68's came with one relay. I have read that the reason they went to two was that the single one didn't pass enough air to make the lights open fast enough. We are probably all used to the speed of thirty year old lights, so can't ell the difference.
And by the way, since I am kind of anal, I work on my lights until they come up pretty much together.
Larry
And by the way, since I am kind of anal, I work on my lights until they come up pretty much together.
Larry
[QUOTE=VetteSpecialties]...I hate to interrupt all the "Klunk"ing, but I wanted to mention that 68's came with one relay. I have read that the reason they went to two was that the single one didn't pass enough air to make the lights open fast enough....[/QUOTE]
Correct. Only one relay valve on a '68 which tees to the left and right headlight doors. On my '68, the RH is about a half a second slower than the left going up. They both come down more or less together. More or less. About that. Somewhat. I've learned to live with it.
I am not sure how to do it, but You hook up one relay and them time it, hook the other up by itself time it. This would give an idea which relay could be bad.
in Forum: C3 Body
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