79 headlight vacuum problem progress
Thread Starter
Drifting
Joined: Jun 2004
Posts: 1,881
Likes: 9
From: staten island ny
79 headlight vacuum problem progress
Started out with drivers side headlight coming up after about 5-7 seconds and the passenger side coming up after 10-12 secs. Started the vacuum diagnostics found in corvette faq and discovered a problem in the pass side relay. Got my new one this a.m from The Last Detail corvette parts, 45 bux was cheapest I found. After installing it my "drivers" side light now comes up instantaneously, or as quick as c3's are capable of. Passenger side still lags behind several seconds. Strange that the drivers side performance was affected by the pass side relay. Will now move on to new boots and seals for the actuators. Also going to test the headlight switch and the hold open because still when I turn on the headlights the a/c flows out the floor duct and no longer out of the dash. I'll figure it out if I have to replace everything. Also did a doc rebuild vacuum kit. Nice to make a little progress anyway.
Happy Motoring, ESU in NY
Happy Motoring, ESU in NY
Burning Brakes
Joined: Oct 2003
Posts: 1,097
Likes: 0
From: Olive Branch MS
St. Jude Contributor
At the risk of having this post sent to general, we are on our fourth. Beautiful animals and great with my kids. Good job on the headlights (just to keep us honest). 
Instructor
Joined: May 2005
Posts: 245
Likes: 5
From: Layton, UT
I am having a headlight problem in my 80 as well. Mine are up and won't come down. I having been tracing the vacuum lines and i have noticed that the line has vacuum when it runs into the relays- but the lines below it don't seem to have any when i pull the hoses- so i don't know if the relay is seized or what. I just can't imagine that both relays would have the exact same problem- usually its one or the other isn't it?
Burning Brakes
Joined: Jun 2002
Posts: 837
Likes: 3
From: Texas
Originally Posted by dyanisis2
I am having a headlight problem in my 80 as well. Mine are up and won't come down. I having been tracing the vacuum lines and i have noticed that the line has vacuum when it runs into the relays- but the lines below it don't seem to have any when i pull the hoses- so i don't know if the relay is seized or what. I just can't imagine that both relays would have the exact same problem- usually its one or the other isn't it?
http://209.183.231.72/corvette-101/vacuum.htm
Instructor
Joined: May 2005
Posts: 162
Likes: 0
From: Lady Lake FL
I recently fixed a 77 for a customer that was having a problem with the lights staying up. All that needed to be replaced were both of the vacuum relays, the internal seals had dried out and they were causing it to leak vacuum. The lights now "fly" up and down. We hooked a vacuum pump for bleeding brakes to each of the relays and neither one would hold a vacuum.
The big line in the middle of the bottom three that goes to the vacuum canister should have vacuum if the engine is running, if not check the line going to the canister from the engine.
KC-Shadetree Performance
I am having a headlight problem in my 80 as well. Mine are up and won't come down. I having been tracing the vacuum lines and i have noticed that the line has vacuum when it runs into the relays- but the lines below it don't seem to have any when i pull the hoses- so i don't know if the relay is seized or what. I just can't imagine that both relays would have the exact same problem- usually its one or the other isn't it?
KC-Shadetree Performance
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