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77 Headlights Question

Old 07-31-2016, 01:30 PM
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xkeots
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Default 77 Headlights Question

On my 77 I recently got my headlights vacuum system finally working. I was curious (I can't remember how my new 77 worked) as my headlights open one at a time then close together. They open about when one is half open the other starts to open. Is that ok and should I just leave them or do I still have to adjust something?
Thanks
Jax
1977 L-82
Old 07-31-2016, 03:32 PM
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Dave J
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When the headlights do not open, normally there is a massive vacuum leak or there is a big mistake in the vacuum hose routing.

When headlights open slowly, or not at the same time, there IS a slow to moderate vacuum leak. Is the slower leak a big deal? Not really if all you want is the headlights come up so the car can be driven at night.

It is an issue if you want the vacuum system to hold vacuum after the car is turned off, and/or if you want atmosphere into the combustion system only to come through the carburetor.

Slow, or only one headlight at a time is a symptom of leaking seals in the actuator(s), relay(s), or both.
Old 07-31-2016, 07:31 PM
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DUB
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It is a vacuum leak...more than likely... and NOT a binding door.

DUB
Old 08-03-2016, 12:14 PM
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Originally Posted by Dave J
When the headlights do not open, normally there is a massive vacuum leak or there is a big mistake in the vacuum hose routing.

When headlights open slowly, or not at the same time, there IS a slow to moderate vacuum leak. Is the slower leak a big deal? Not really if all you want is the headlights come up so the car can be driven at night.

It is an issue if you want the vacuum system to hold vacuum after the car is turned off, and/or if you want atmosphere into the combustion system only to come through the carburetor.

Slow, or only one headlight at a time is a symptom of leaking seals in the actuator(s), relay(s), or both.
New relays, actuators and all new vacuum hoses. No leaks unless when I had my arm behind headlamp switch i loosened one, but I don't hear any hissing.
Jax
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Last edited by xkeots; 08-03-2016 at 12:16 PM.
Old 08-03-2016, 12:31 PM
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Peterbuilt
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Test the actuators and relays.

http://www.corvette-101.com/vacuum.htm
Old 08-03-2016, 06:46 PM
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Dave J
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New relays, actuators and all new vacuum hoses. No leaks unless when I had my arm behind headlamp switch i loosened one, but I don't hear any hissing.
As many on here have found, new does not mean good. You will also generally not hear "hissing" because the system is not "charged", the opposite is true. If a vacuum component is "leaking", it is actually allowing atmosphere (air) into the system where it shouldn't.

This is how I test headlight/wiper door relays



Old 08-03-2016, 06:51 PM
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I agree..I test each actuator relay before I install it and I actually have had some go bad in a few months.

DUB

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