Headlight will only go down when engine off
Thread Starter
Intermediate
Joined: Jun 2013
Posts: 27
Likes: 0
Headlight will only go down when engine off
Ok here is another question on vacuum issues with headlights. I didn't see this exact problem on headlight actuation. If its there please point me in the right direction.
My headlights on my 71 Vette come on just fine but my right light will not go down until I cut the engine off. Any suggestions will be greatly appreciated. Thanks.
My headlights on my 71 Vette come on just fine but my right light will not go down until I cut the engine off. Any suggestions will be greatly appreciated. Thanks.
Last edited by skilew; Mar 23, 2015 at 11:32 AM.
Thread Starter
Intermediate
Joined: Jun 2013
Posts: 27
Likes: 0
Le Mans Master
Joined: Aug 2006
Posts: 7,419
Likes: 1,555
From: mount holly NC
2025 c3 ('74-'82) of the Year Finalist - Unmodified
2019 C3 of Year Finalist (appearance mods)
Thread Starter
Intermediate
Joined: Jun 2013
Posts: 27
Likes: 0
Team Owner
Joined: Sep 2006
Posts: 31,200
Likes: 4,287
From: Westminster Maryland
Hi S,
There are 2 relays mounted to the underside of the hood surround between the head lights.
Reverse the hoses running from the relays to the headlights, (large green and red hoses), so the left side relay is now controlling the right side headlight, and visa-versa.
If the problem switches to the left headlight you'll know there's a problem with the right side relay.
Then you can test the operation of the faulty relay with a vacuum pump/gauge like a mityvac.
Good Luck!
Regards,
Alan
The location of the relays and the large green and red hoses. The horn is partially blocking the view of the left side relay.
There are 2 relays mounted to the underside of the hood surround between the head lights.
Reverse the hoses running from the relays to the headlights, (large green and red hoses), so the left side relay is now controlling the right side headlight, and visa-versa.
If the problem switches to the left headlight you'll know there's a problem with the right side relay.
Then you can test the operation of the faulty relay with a vacuum pump/gauge like a mityvac.
Good Luck!
Regards,
Alan
The location of the relays and the large green and red hoses. The horn is partially blocking the view of the left side relay.
Thread Starter
Intermediate
Joined: Jun 2013
Posts: 27
Likes: 0
Hi S,
There are 2 relays mounted to the underside of the hood surround between the head lights.
Reverse the hoses running from the relays to the headlights, (large green and red hoses), so the left side relay is now controlling the right side headlight, and visa-versa.
If the problem switches to the left headlight you'll know there's a problem with the right side relay.
Then you can test the operation of the faulty relay with a vacuum pump/gauge like a mityvac.
Good Luck!
Regards,
Alan
The location of the relays and the large green and red hoses. The horn is partially blocking the view of the left side relay.
There are 2 relays mounted to the underside of the hood surround between the head lights.
Reverse the hoses running from the relays to the headlights, (large green and red hoses), so the left side relay is now controlling the right side headlight, and visa-versa.
If the problem switches to the left headlight you'll know there's a problem with the right side relay.
Then you can test the operation of the faulty relay with a vacuum pump/gauge like a mityvac.
Good Luck!
Regards,
Alan
The location of the relays and the large green and red hoses. The horn is partially blocking the view of the left side relay.
Team Owner
Joined: Sep 2006
Posts: 31,200
Likes: 4,287
From: Westminster Maryland
Hi S,
I believe so.
If not unscrew the relays from their mount plate so they'll just hanging and can be pulled to the side.
The alternative is to test the relay in place.
Do you have a mity-vac?
Regards,
Alan
I believe so.
If not unscrew the relays from their mount plate so they'll just hanging and can be pulled to the side.
The alternative is to test the relay in place.
Do you have a mity-vac?
Regards,
Alan
Corvette Stories
The Best of Corvette for Corvette Enthusiasts
150 hp to 1,250 hp: Every Corvette Generation Compared by the Specs That Matter
Joe Kucinski
8 Coolest Corvette Pace Cars (and Replicas) of All Time
Verdad Gallardo
Top 10 Corvette Engines RANKED by Peak Torque (70+ Years of Muscle!)
Joe Kucinski
Corvette ZR1X Will Be Pacing the Indy 500, And Could Probably Race, Too!
Verdad Gallardo
Top 10 Corvettes Coming to Mecum Indy 2026!
Brett Foote
Top 10 C9 Corvette MUST-HAVES to Fix These C8 Generation Flaws!
Michael S. Palmer
10 Revolutionary 'Corvette Firsts' Most People Don't Know
Joe Kucinski
5 Reasons to Upgrade to an LS6-Powered Corvette; 5 Reasons to Stay LT2
Michael S. Palmer
2027 Corvette vs The World: Every C8 vs Its Closest Competitor
Joe Kucinski
Drifting
Joined: Jul 2006
Posts: 1,259
Likes: 154
From: Deplorableville Nebraska
The relay has a piston inside it's bore that is raised and lowered by the control chamber on top. If the rubber piston is leaking around the seal, you will have a vacuum leak. The leak could be minor or completely blown. Any leak will cause problems.
Simple quick way to test the relay is to connect your hand held vacuum pump to the middle port, and block the lower port with your finger or a short section of blocked vacuum hose. Pump it up and the relay should hold vacuum and not leak over time.
Simple quick way to test the relay is to connect your hand held vacuum pump to the middle port, and block the lower port with your finger or a short section of blocked vacuum hose. Pump it up and the relay should hold vacuum and not leak over time.
Thread Starter
Intermediate
Joined: Jun 2013
Posts: 27
Likes: 0
I think I found my problem by discovering another problem. My wiper door has not work for some time. I believe it is the "witch hat" actuator. Last night I plugged both lines feeding the actuator trying to trouble shoot that problem and then I just decided to recheck my headlight issue and they both worked perfectly. The loss of vacuum through the wiper acuator must have been affecting my headlight actuation or for some other reason my haedlights are now working.
Team Owner
Joined: Sep 2006
Posts: 31,200
Likes: 4,287
From: Westminster Maryland
Hi s,
Maybe?
The large hose supply for the headlight and wiper door actuators are interconnected by a 'T' in the yellow striped hose very near the vacuum reserve tank.
So could be!
Regards,
Alan
Maybe?
The large hose supply for the headlight and wiper door actuators are interconnected by a 'T' in the yellow striped hose very near the vacuum reserve tank.
So could be!
Regards,
Alan
Thread Starter
Intermediate
Joined: Jun 2013
Posts: 27
Likes: 0