1970 Corvette Headlight Operation
Thread Starter
Intermediate
Joined: Feb 2008
Posts: 43
Likes: 0
From: Hewitt New Jersey
1970 Corvette Headlight Operation
Long winter here in NJ. Car finally out. Last year I asked why my headliughts stayed open. Found the line to the hedlight switch was off and reconnected it. Viola!
Anyway now I have another issue. Put the headlights up. The driver's side goes up well, and the passenger side follows...slowly, but goes up as well.
BUT...when I pull into the garage, with the car running, and depress the headlight switch, the driver's side remains open. If I shut the car off, it stays the same. IF I get out of the car, with it still running, and the headlight switch depressed, I can grab the headlight door edge, lifting it ever so slightly, and it closes right away.
Thanks,
Dennis
Anyway now I have another issue. Put the headlights up. The driver's side goes up well, and the passenger side follows...slowly, but goes up as well.
BUT...when I pull into the garage, with the car running, and depress the headlight switch, the driver's side remains open. If I shut the car off, it stays the same. IF I get out of the car, with it still running, and the headlight switch depressed, I can grab the headlight door edge, lifting it ever so slightly, and it closes right away.
Thanks,
Dennis
Melting Slicks
Joined: Apr 2007
Posts: 3,189
Likes: 111
From: Tolland CT
I would check for vacuum leaks. To do this I used a hand held vacuum pump with a gauge as found with a brake bleeding kit. Start with the actuators, you should be able to pull a vacuum and hold it on either side of the can. If not, could be a seal. Next in line are the vacuum relays, two under the surround, ahead of the hood. Both of mine leaked like sieves. Connect the vacuum pump to the large port in the center, block the other two, should be able to hold a vacuum.
You could take a step back if you prefer to test the overall system by finding the main vacuum line going to the headlights, disconnect from the tee, connect the pump and try to pull a vacuum. You can narrow down the source of the leak by pinching the lines at strategic spots.
There's another relay on your firewall, near the brake booster or master cylinder which controls the wiper door. Another source of leaks.
My experience was all three relays leaked. My actuators, hoses, and tank were okay. Once I replaced my relays, all headlights and wiper door became very responsive. Some vendors supply a diagram of the vacuum hoses, makes tracing easier.
You could take a step back if you prefer to test the overall system by finding the main vacuum line going to the headlights, disconnect from the tee, connect the pump and try to pull a vacuum. You can narrow down the source of the leak by pinching the lines at strategic spots.
There's another relay on your firewall, near the brake booster or master cylinder which controls the wiper door. Another source of leaks.
My experience was all three relays leaked. My actuators, hoses, and tank were okay. Once I replaced my relays, all headlights and wiper door became very responsive. Some vendors supply a diagram of the vacuum hoses, makes tracing easier.
Racer
Joined: Jun 2011
Posts: 300
Likes: 3
From: kempton park Gauteng
Headlight doors
Hi ,
Whilst you most likely do have some form of leak in your system which is not the quickest thing to find other than a cracked or broken pipe , i would say from your description of the fault and the way you get the flap to close, the issue is more to do with a sticking mecanism.
Try a tin of lube spray Q 20 or the like and spray the pin and the bushings of the sticking unit , these do get dirty and they do not slide properly . It may be a cheaper start and less time consuming . If this doesnt help i suggest you get yourself a Mitty Vac and start testing each individual component one by one in the system . Willcox have a great write up on how to check each part . Its not really hard to find the issues , just time consuming .
All the best ,
John
Whilst you most likely do have some form of leak in your system which is not the quickest thing to find other than a cracked or broken pipe , i would say from your description of the fault and the way you get the flap to close, the issue is more to do with a sticking mecanism.
Try a tin of lube spray Q 20 or the like and spray the pin and the bushings of the sticking unit , these do get dirty and they do not slide properly . It may be a cheaper start and less time consuming . If this doesnt help i suggest you get yourself a Mitty Vac and start testing each individual component one by one in the system . Willcox have a great write up on how to check each part . Its not really hard to find the issues , just time consuming .
All the best ,
John
Long winter here in NJ. Car finally out. Last year I asked why my headliughts stayed open. Found the line to the hedlight switch was off and reconnected it. Viola!
Anyway now I have another issue. Put the headlights up. The driver's side goes up well, and the passenger side follows...slowly, but goes up as well.
BUT...when I pull into the garage, with the car running, and depress the headlight switch, the driver's side remains open. If I shut the car off, it stays the same. IF I get out of the car, with it still running, and the headlight switch depressed, I can grab the headlight door edge, lifting it ever so slightly, and it closes right away.
Thanks,
Dennis
Anyway now I have another issue. Put the headlights up. The driver's side goes up well, and the passenger side follows...slowly, but goes up as well.
BUT...when I pull into the garage, with the car running, and depress the headlight switch, the driver's side remains open. If I shut the car off, it stays the same. IF I get out of the car, with it still running, and the headlight switch depressed, I can grab the headlight door edge, lifting it ever so slightly, and it closes right away.
Thanks,
Dennis
Burning Brakes
Joined: Jun 2013
Posts: 1,076
Likes: 148
From: Hunterdon Cty NJ
I too have a 70 and the lights went up and down fine untill one day one stayed up. I found the shroud(?) bezel(?) around the lights lost some screws and was hitting the body not allowing the light to drop. I found some screws that would work and that fixed it. I have since bought a completer screw kit for the bezels, but have yet to put them in. And BTW nice to hear of another NJ 70 Vette.
Race Director
Joined: Jul 2015
Posts: 13,082
Likes: 3,399
From: SW Florida.
When your headlights go up slowly, it is an air problem not a vacuum problem. The vacuum sucks. The air out of one side of the diaphragm and atmospheric pressure has to flowin to the other side and push the headlight up. You got a bug nest blocking the airflow for the air to go in to raise the headlights. It’s the smile shape in the picture above. A lot of other problems are vacuum blockages not just vacuum. Leaks. Take all the hoses off both ends and blow them out. Do not suck them out. Blow them out. If you suck on it since it’s a vacuum line to see if it passes vacuum, you’re going to inhale pieces of dead bugs. And dead bug nests. And other **** that has been in there for 40 some years.
Advanced
Joined: Jan 2020
Posts: 81
Likes: 47
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