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I know you guys can't get enough headlight questions! I figured that instead of spending however long trying to track the issue down, I'll just ask. I'm betting someone knows right off the top of their head what's wrong.
1981 Vette.
So, my lights used to come up slowly, one at a time. Now, they don't come up at all. They go down just fine.
Here's the kicker: if I go out and lift the driver side light up, as soon as it reaches its fully open position, the passenger side light pops up like somebody goosed it.
2020 Corvette of the Year Finalist (performance mods)
2019 C3 of Year Winner (performance mods)
2016 C3 of Year Finalist
big enough leak that when you get the first light open it closes th eleak and the other gets vacuum. Try disconnecting one and plugging the hose at the T, then the other. THat should tell you if its one or the other. If it isnt in the "work " side, then try the signal side, do th e same thing att the T where th evacuum splits.
2020 Corvette of the Year Finalist (performance mods)
2019 C3 of Year Winner (performance mods)
2016 C3 of Year Finalist
So on the white hose goiing to the relays, seperate the systems at the T and see if they both pop open. Then reattach one side at a time and plug the other hose and cycle your headlight switch to see what happens. Releasing the vacuum from the switch opens the doors, giving vacuum closes them. If the cause is on only one side you'll see which side it is
you can see here that when you introduce atmospheric pressure to hoses 3, the spring pushes the actuators towards the blue side which changes which side of the actuator sees vacuum.
So most likely either the relay isnt releasing the vacuum and internnal valve to get the relay to transfer the vacuum or the relay is leaking too much vacuum before it has a chance to transfer the vacuum inside the actuator. Doesnt really matter if you can get one side working, then you'll be able to figure out the other. Trust me and try one side at a time and you'll see what is up. Could be multiple leaks on both side as well. (the actuator and the relay)
Last edited by Rescue Rogers; Jun 30, 2020 at 05:23 PM.
I'll venture that the shaft seals around the vacuum motors are leaking severely. Fortunately new shaft seal kits are readily available.
You really need a hand vacuum pump like a Mityvac to troubleshoot. Another very common problem are stretched hose ends that cause minor leaks throughout the system. Some should be long enough that you can cut 3/8" or so off the ends but like all 30 year-old rubber items in the car it's really time for replacement. Look up Doc Rebuild for excellent vacuum hose kits for every system in the car. Both the inner and outer diameters of the hoses matters for those connecting to the vacuum relays so you must use the proper lines! They're not the sort of things you'll find at a local auto parts store.
If your car still has the original CCC computer control system and associated carburetor vacuum leaks are are a very common source of nasty problems.
A hand vacuum pump will take forever to suck down a headlamp actuator. Yes it will work (if leakage is minimal...and your pump hand doesn't give out!); but creating vacuum with a really big air pump....like a Chevy engine....is the easiest way to do vacuum tests.
A hand vacuum pump will take forever to suck down a headlamp actuator. Yes it will work (if leakage is minimal...and your pump hand doesn't give out!); but creating vacuum with a really big air pump....like a Chevy engine....is the easiest way to do vacuum tests.
I have to disagree. My Mityvac works perfectly for testing individual components and it takes only a few pumps for even that big headlamp door motor. It's also easy to pump down the entire HVAC system. The entire headlamp system is another matter--particularly with the huge framing member that doubles as the vacuum reservoir in later C3s. That will leave your hand aching--I know...
Well, I haven't had a chance to dig into things yet. I hope to do so today or tomorrow. Can't complain, though, since I was out of work for a month and a half! Working with a 1-hour commute kind of robs a lot of play time.
Maybe I'll just take everything out and give it a good coat of Flex-Seal!
ANOTHER headlight question!
