1976 - Headlights won't close
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Joined: Jan 2008
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From: Greenville Oh
1976 - Headlights won't close
Been working on buying a 1976 Corvette and one of the problems is that the headlights are open and will not close. I've done a fair amount of shadetree mechanic work (not on Corvettes) but have never delt with something like this. Since we are still negotiating price I want to have some idea as to what the possible, or worse, problem there could be that is causing the headlights to not function correctly. And of course, best guess on cost of repair. I know they work off vacum which sounds inexpensive to repair but I don't want to make a big $$$ mistake here. Thanks
Team Owner
Joined: Aug 2006
Posts: 24,125
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From: Columbia Missouri
If they both stay open it's probably not a mechanical issue, and vacuum related. All in all, vacuum problems are hard to trace but not too hard to fix and not a lot of money has to go into it either unless it's an actuator.
Also, it could be that there was a vacuum problem so the previous owner locked the lights in the up position. There are 'knees' that hold the lights up, and the actuators move these knees in and out to raise and lower the lights. These knees can be locked backwards, like hyper extending them, so the lights always stay up.
If the lights are the biggest problem, then you have little to worry about. Big concerns should be the history, frame, birdcage, brakes, suspension, drive train, and interior.
Also, it could be that there was a vacuum problem so the previous owner locked the lights in the up position. There are 'knees' that hold the lights up, and the actuators move these knees in and out to raise and lower the lights. These knees can be locked backwards, like hyper extending them, so the lights always stay up.
If the lights are the biggest problem, then you have little to worry about. Big concerns should be the history, frame, birdcage, brakes, suspension, drive train, and interior.
TheCorvetteBen
Joined: Feb 2007
Posts: 4,987
Likes: 144
From: Van Alstyne, TX
My car had the same problem. After i pulled the lights up by hand, drove around, and then shut the car off, the lights would stay up. It turned out that i had a bad actuator seal. After about a half hour of work, and a $6 rubber part, my headlights work perfectly. No other issue. From what i have read it could be a simple cheap fix (like mine) or something more expensive, but either way it wont bust your wallet.
Drifting
Joined: Sep 2001
Posts: 1,427
Likes: 1
From: Boxford Mass
Good to check that, its located under the steering wheel between your knees. Nothing vacuum related is terrible from a cost perspective. They can be difficult to trace. I bought a cheap medical vacuum pump on ebay for $20 that pulls 20 inches -- perfect for diagnosing problems so you dont have to keep your car running all the time.
The headlight switch in the dash is a PITA to change. There is a good vacuum troubleshooting guide available also.
The headlight switch in the dash is a PITA to change. There is a good vacuum troubleshooting guide available also.
Team Owner
Joined: Jan 2006
Posts: 37,637
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From: Crossville TN
It is unlikely that the headlight switch is the cause of your problem. The headlights stay up if:
1. The manual "Headlights UP" valve [under the steering column] is left in the 'open' position;
2. Someone has swaped the positions of the "open" and "close" vacuum lines on the headlight actuators...so they would stay open;
3. There are vacuum leaks/line errors that cause the headlights to stay open.
Usually, finding a good car with vacuum "problems" is a GOOD thing...because the present owner doesn't know how to deal with it and will discount the price to be rid of the headaches. But, fixing C3 vacuum line problems is almost always inexpensive...the acuators [which are not cheap] are rarely the problem...most often it is minor components, hoses left open, vacuum reservoir leaky, etc. Buy a vacuum diagram and troubleshooting guide for $10 [Corvette aftermarket supply] and a vacuum gauge for $25 at your local parts store. Read up on how to test the system and go for it. If you need specific help once you get started, put a post on this Forum. Good luck.
1. The manual "Headlights UP" valve [under the steering column] is left in the 'open' position;
2. Someone has swaped the positions of the "open" and "close" vacuum lines on the headlight actuators...so they would stay open;
3. There are vacuum leaks/line errors that cause the headlights to stay open.
Usually, finding a good car with vacuum "problems" is a GOOD thing...because the present owner doesn't know how to deal with it and will discount the price to be rid of the headaches. But, fixing C3 vacuum line problems is almost always inexpensive...the acuators [which are not cheap] are rarely the problem...most often it is minor components, hoses left open, vacuum reservoir leaky, etc. Buy a vacuum diagram and troubleshooting guide for $10 [Corvette aftermarket supply] and a vacuum gauge for $25 at your local parts store. Read up on how to test the system and go for it. If you need specific help once you get started, put a post on this Forum. Good luck.
Drifting
Joined: Jul 2006
Posts: 1,871
Likes: 6
From: Sault Ste. Marie Ontario
Pull the vacuum hose off the back of the actuator and try to push the light asembly down into position. If it moves up and down freely, chances are it is not a mechanical issue (bound bearings, broken springs etc.) and you can chase the vacuum system.
I just purchased the assembly rebuild components for my system which included actuators, relays, hoses, bushings etc. and the bill came in around $600
I just purchased the assembly rebuild components for my system which included actuators, relays, hoses, bushings etc. and the bill came in around $600
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Team Owner
Joined: Jan 2006
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From: Crossville TN
Just curious, eastltd... Did you NEED to replace all of those components or did you CHOOSE to replace them because you wanted all new stuff? How much of the stuff removed was actually defective? It's very unusual to have all those things turn out defective [unless in a fire].
Burning Brakes
Joined: Oct 2005
Posts: 845
Likes: 1
From: Columbus Indiana
Wait!
Don't you have to pull foward on the locking 'knee' first before you get too enthusiastic about applying down pressure?John
Last edited by seventysixvette; Feb 1, 2008 at 07:17 PM. Reason: still learnin to spell......
Drifting
Joined: Jul 2006
Posts: 1,871
Likes: 6
From: Sault Ste. Marie Ontario
Just curious, eastltd... Did you NEED to replace all of those components or did you CHOOSE to replace them because you wanted all new stuff? How much of the stuff removed was actually defective? It's very unusual to have all those things turn out defective [unless in a fire].
Drifting
Joined: Jul 2006
Posts: 1,871
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From: Sault Ste. Marie Ontario
Team Owner
Joined: Aug 2006
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From: Columbia Missouri
I have before, but that was because I locked the knees so the headlights would always stay up. This was on a different '77 which had some serious vacuum problems. The knees were pushed forward, hyper extending them, and locking them. In order to get them down I had to pull the knees back towards the front, unlocking them. IF the previous owner locked the knees to avoid having to work on the headlight, they would have to be unlocked to allow the lights to fall.
Race Director
Joined: Jul 2001
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Burning Brakes
Joined: Oct 2005
Posts: 845
Likes: 1
From: Columbus Indiana
That's kinda what I thought. I still have my headlight assemblies out of the car since a complete rebuild. I checked last night, I have the actutators adjusted to push the joint slightly over center so they lock everytime they're opened.
I thought the linkage locking was why you always read in the manuals
*Never try to force the headlight doors closed*
John
Last edited by seventysixvette; Feb 2, 2008 at 01:35 PM.
Team Owner
Joined: Aug 2006
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From: Columbia Missouri
Race Director
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From: Tampa, Florida
Melting Slicks
Joined: Jul 2004
Posts: 2,577
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From: Long Island New York
More than likely it's the relays. Mine used to do the same thing. I replaced all the vacuum lines, check valve, and filter and they still didn't work so next I replaced the seal in the actuators even though they tested good, still nothing. My relays tested good as well so I thought maybe my vacuum tank had a leak. nope no leak and now I'm getting frustrated. Finally I decided the replace the relays even thought they tested Ok. I figured why not, I've replaced everything else at this point. Well after replacing them and starting My car, I pulled out the headlight switch and they both jumped right up, pushed the switch back in and bingo they both went right down. I test the override switch and that works fine. Now my lights works just like they did when they left the factory.
Team Owner
Joined: Aug 2006
Posts: 24,125
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From: Columbia Missouri
The vacuum is drawn into the engine, and the reservoir is just a big space vacuum close to the headlights. The engine sucks air out of the system and the tank is at the end of that system, which is where the headlight relays connect.
Here is a diagram, that has a slight misprint at the top. The vacuum tube that crosses over from the switch to the cutoff is wrong. The other tube crosses over.
