vaccum headlights
Thread Starter
Cruising
Joined: Jun 2011
Posts: 14
Likes: 0
From: Terrace B.C.
vaccum headlights
good morning. I am new to this forum and i am a first time corvette owner. a red 76. last nite i was triing the headlights and they would not come up. i was looking under hood and when i diconnected one vac hose they came up and would not go down till i plugged the hose in. wierd i thought. let me say when a bought the car 1 week ago they did go up and down. there is a hissing sound in the dash when i pull the lights on any help would be appreciated thank you Terry
Melting Slicks
Joined: Mar 2008
Posts: 2,023
Likes: 6
From: Austin Tx
The easiest way to think about how the headlight vacuum system works, is to understand that it works pretty much the same as an system with an electric relay.
This diagram might help you understand how it works.
This diagram might help you understand how it works.
Safety Car
Joined: Oct 2007
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From: Austin Texas
Corvette of the Year Winner 2017
2016 C3 of Year Finalist
following the hissing noise, find the vacuum hose,
let the hose lay nature, and it should point you to the port
it should be connected to.
let the hose lay nature, and it should point you to the port
it should be connected to.
Le Mans Master
Joined: Mar 2008
Posts: 5,948
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From: Oxford MA-----You just lost the game!!!!
If you are new to C3 Corvettes, the vacuum operated headlight system seems really weird and confusing, but it's really not. Spend a little time getting to know how it works, and you will find that it is really quite simple and ingenious. Here is a great paper that does a great job of explaining how it all works.
http://fedbizoppssearches.com/CFImag...umTutorial.pdf
Scott
http://fedbizoppssearches.com/CFImag...umTutorial.pdf
Scott
Last edited by scottyp99; Jun 22, 2011 at 03:41 PM.
Melting Slicks
Joined: Mar 2006
Posts: 3,342
Likes: 7
From: Connecticut
If the lines are connected and not cracked/leaking then It would most likely be in need of a new manual (over ride) valve.
You could temporarily hook the hoses together bypassing the valve with a small piece of tubing to eliminate the leak.
Any vacuum leaks will cause the engine to idle rough.
Team Owner
Joined: Jan 2006
Posts: 37,637
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From: Crossville TN
The headlight switch should also be included in that schematic. It is electrical (to turn on the lamps) and vacuum (for raising/lowering the headlamps). The pull-down switch under the steering column is an "override" switch that will keep the headlights in the "UP" position. I suspect that the override switch has been pulled down and will not allow the lights to close. Push that under-dash switch up and see if it works.
If so, great; but you still have a vacuum leak under the dash somewhere. It should be found and fixed/reconnected.
If so, great; but you still have a vacuum leak under the dash somewhere. It should be found and fixed/reconnected.
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Team Owner
Joined: Jan 2006
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From: Crossville TN
Ah...the headlight switch in the schematic above is drawn exactly like the manual override valve. From a schematic perspective, that is correct, although in reality, that is built into the headlight switch mechanism. Thanks for the 'head's up', Roger.
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