Vacuum Problem; Down Yes----Up? No......
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From: Omaha NE
Vacuum Problem; Down Yes----Up? No......
I recently purchased a 1978 Corvette L-48, and one of the problems I am having with it is with the headlight system. With the vacuum hoses connected, I can get the headlights to lower, but not raise again... I have checked for vacuum leaks, and have not found any yet...(I have not put a guage on the hoses, but I do feel vacuum pressure.) Can anyone help me track down the problem? I suspect I may need new seals in both the headlight actuators, but I would welcome any advice on the best way to proceed in troubleshooting/order of parts replacement... :confused:
Thank you to all who reply.... :yesnod:
Thank you to all who reply.... :yesnod:
Drifting
Joined: Aug 2002
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From: Marietta Ga.
Re: Vacuum Problem; Down Yes----Up? No...... (Trevelisek)
Do a search thru the archives here and check coevettefaq also. This has been covered a good bit and you could find your answer there. Do they come up when you turn on the lights and not go down when off, how about the over ride switch?
Melting Slicks
Joined: Dec 2000
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From: Eastern Connecticut
Re: Vacuum Problem; Down Yes----Up? No...... (72GACRZR)
It must be the design of the linkage that makes lowering easier than raising. Depending on how well my engine is idling (amount of vacuum) I sometimes have to help the headlights up, but they always pop right down. It's probably related, but the override doesn't work, just hisses when I pull it down. You probably have a vacuum leak (maybe at the actuator). Joe
Drifting
Joined: Aug 2002
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From: Marietta Ga.
Re: Vacuum Problem; Down Yes----Up? No...... (joe73vette)
I sometimes have to help the headlights up, but they always pop right down.
Le Mans Master
Joined: Aug 2001
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From: Standing still with all my might Texas
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Re: Vacuum Problem; Down Yes----Up? No...... (Trevelisek)
I would suspect the seals on the actuators are your problem, they only seal the up (extend) side of the unit. The down (retract) side will only leak if the internal diaphram has a hole in it, and then it would leak on both up and down. confused yet? :crazy:
To eliminate the relays as the problem you might try swithcing the top and bottom hoses on the relay, this will reverse the acutation of the headlight (i.e. with the switch in the on position the lights should go down, with the switch in the off position the lights should go up).
If the lights open on thier own now and will not close then the problem is with the relay. If ther lights will still only go down and not up, then the problem is in the relay.
I spent 4 hours last night finally de-bubbafying my headlights and installing a new actuator on the drivers side. They can be a real PITA!
Good luck :cheers:
To eliminate the relays as the problem you might try swithcing the top and bottom hoses on the relay, this will reverse the acutation of the headlight (i.e. with the switch in the on position the lights should go down, with the switch in the off position the lights should go up).
If the lights open on thier own now and will not close then the problem is with the relay. If ther lights will still only go down and not up, then the problem is in the relay.
I spent 4 hours last night finally de-bubbafying my headlights and installing a new actuator on the drivers side. They can be a real PITA!
Good luck :cheers:
Drifting
Joined: Sep 2001
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From: Boxford Mass
Re: Vacuum Problem; Down Yes----Up? No...... (Kevin_73)
If its both headlamps, then I'd check the control system. Does your override switch work when you pull it down? They should pop up at that point.
Try pulling a line to the override switch and see that makes them go down. If it does, its probably two bad switches.
Otherwise, its two bad actuators or relays. Tough one -- combo problem.
Keep at it, you'll nail it.
Try pulling a line to the override switch and see that makes them go down. If it does, its probably two bad switches.
Otherwise, its two bad actuators or relays. Tough one -- combo problem.
Keep at it, you'll nail it.
Burning Brakes
Joined: Jun 2002
Posts: 837
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From: Texas
Re: Vacuum Problem; Down Yes----Up? No...... (74jack)
http://www.corvette-101.com/index.htm
click vacuum trouble
You might have to click on "corvette-101 home page" first.
[Modified by rip74, 1:37 AM 10/10/2002]
click vacuum trouble
You might have to click on "corvette-101 home page" first.
[Modified by rip74, 1:37 AM 10/10/2002]
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From: Lenoir City Tennessee
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Re: Vacuum Problem; Down Yes----Up? No...... (rip74)
Thanks for the diagram Rip. It is close enough for me to get started anyway. I printed yours and will search for the rest of the diagram for the 70 model. :cool:
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From: Omaha NE
Re: Vacuum Problem; Down Yes----Up? No...... (Trevelisek)
First of all, I would like to thank all the people out there who took the time to reply to my queries; you have been more than kind! :cheers:
I tried to reverse the green and red lines to both relays with the headlights up....the headlights would stay up when I had the motor running, but when I pulled the override switch into the on position they went down. (so far so good)
When I turn the override switch back off, though, the headlights do not go back up....I guess I am just going to have to break down and do a little "transplanting" from my '76 to see if I can isolate the problem at the relay....I'll post the results if it works....
Thanks again to all! (Also thanks for the t-top help)
:seeya
I tried to reverse the green and red lines to both relays with the headlights up....the headlights would stay up when I had the motor running, but when I pulled the override switch into the on position they went down. (so far so good)
When I turn the override switch back off, though, the headlights do not go back up....I guess I am just going to have to break down and do a little "transplanting" from my '76 to see if I can isolate the problem at the relay....I'll post the results if it works....
Thanks again to all! (Also thanks for the t-top help)
:seeya
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From: Omaha NE
Re: Vacuum Problem; Down Yes----Up? No...... (Trevelisek)
(Grumph!) :confused:
I just pulled the left-hand relay from my 1978 (The one with the headlight problem) and switched in a relay from my 1976 (Where the headlights DO raise and lower). I got no change in the 1978 when I put in the working relay from the 1976. Then I took the relay from the 1978 and hooked it up to the 1976 Corvette....The headlights on the 1976 still come up....
I think this eliminates the vacuum relay...so next I will try replacing the actuator seals...
Does anyone know if ONE relay is bad, would it affect both headlamps or just the one....(I would suspect 99% that it would just be one)
Oh well, I'll keep wrestlin' with it! :boxing
I just pulled the left-hand relay from my 1978 (The one with the headlight problem) and switched in a relay from my 1976 (Where the headlights DO raise and lower). I got no change in the 1978 when I put in the working relay from the 1976. Then I took the relay from the 1978 and hooked it up to the 1976 Corvette....The headlights on the 1976 still come up....
I think this eliminates the vacuum relay...so next I will try replacing the actuator seals...
Does anyone know if ONE relay is bad, would it affect both headlamps or just the one....(I would suspect 99% that it would just be one)
Oh well, I'll keep wrestlin' with it! :boxing
