headlight switch vacuum leak
Thread Starter
Melting Slicks
Joined: Jan 2003
Posts: 3,030
Likes: 94
From: meraux LA
headlight switch vacuum leak
I just got my vacuum hooked up on my light. But I have a vacuum leak in the headlight switch. Put the light on and vacuum leaks out of the switch, Turn off and there is no vacuum leak. So my question is can the leak be fixed or do I need a new switch?
Race Director
Joined: May 2006
Posts: 16,528
Likes: 53
From: Dayton, Ohio
You probably have the 2 hoses reversed,that creates a leak. In this first diagram from Corvette 101 WHICH IS POSTED ALL OVER THE WEB AND STILL IS BEING POSTED the hoses in the red circle show them hooked up BACKWARDS. In the second diagram is the correct way to attach the hoses.
Team Owner
Joined: Jan 2006
Posts: 37,637
Likes: 3,118
From: Crossville TN
Either that or one [or both] hoses have come loose from the switch. I think it is pretty rare {not impossible} that the seal in the headlight switch goes bad. Verify the correct routing and connections first (if you can). Change headlight switch as a last resort. 
Race Director
Joined: Oct 2000
Posts: 12,710
Likes: 3,161
From: Shamong, NJ
If it's one of the repro switches on the market, it's quite possible that it's leaking. There had been a lot of trouble with repro switches about 2 years ago, and I'm sure that some of the bad switches are still flooting around out there.
Melting Slicks
Joined: Sep 2007
Posts: 2,429
Likes: 0
From: Tucson AZ
I had a bad headlight switch when I bought my 69, replaced it, and the vacuum side of the switch came apart. It happens
Race Director
Joined: May 2006
Posts: 16,528
Likes: 53
From: Dayton, Ohio
Last edited by ...Roger...; Sep 28, 2009 at 03:55 PM.
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Le Mans Master
Joined: Aug 2006
Posts: 7,431
Likes: 1,562
From: mount holly NC
2025 c3 ('74-'82) of the Year Finalist - Unmodified
2019 C3 of Year Finalist (appearance mods)
Port 3 gets the blue striped hose, it connects to the bottom port on the pull down switch.
Thread Starter
Melting Slicks
Joined: Jan 2003
Posts: 3,030
Likes: 94
From: meraux LA
Thanks all, Roger you were right, I had the hoses backwards on the switch. 
Man it feels great, 1st time in 25years I can pull the light switch and have the light come on and up, I never had the vacuum hooked up until after rebuilding due to Katrina. Replaced all the pcs and now it all works like it suppose to.
Man it feels great, 1st time in 25years I can pull the light switch and have the light come on and up, I never had the vacuum hooked up until after rebuilding due to Katrina. Replaced all the pcs and now it all works like it suppose to.
Race Director
Joined: May 2006
Posts: 16,528
Likes: 53
From: Dayton, Ohio
Team Owner
Joined: Sep 2006
Posts: 31,335
Likes: 4,451
From: Westminster Maryland
Hi,
I, too, believe the blue hose goes on the #3 nipple..... BUT..... I've been curious about what happens if you move the nipples to the 'wrong' position AND move the blue hose to the #2 nipple.
Did the switch/nipples change at some point and that's why the AIM is wrong?
Regards,
Alan
PS: I'm really only familiar with the 71 AIM, so I'm not sure what years might be right or wrong.
I, too, believe the blue hose goes on the #3 nipple..... BUT..... I've been curious about what happens if you move the nipples to the 'wrong' position AND move the blue hose to the #2 nipple.
Did the switch/nipples change at some point and that's why the AIM is wrong?
Regards,
Alan
PS: I'm really only familiar with the 71 AIM, so I'm not sure what years might be right or wrong.
Le Mans Master
Joined: Aug 2006
Posts: 7,431
Likes: 1,562
From: mount holly NC
2025 c3 ('74-'82) of the Year Finalist - Unmodified
2019 C3 of Year Finalist (appearance mods)
All the years may be wrong!
Hi Alan, here's a page from the 74 AIM, it is wrong too. PG.
Team Owner
Joined: Sep 2006
Posts: 31,335
Likes: 4,451
From: Westminster Maryland
Hi Pete,
Thanks for the picture.
It's interesting in that it appears to be the same drawing as in my 71 AIM, but has been modified with the changes that were needed when the wiper door was dropped.
I don't understand why the problem wasn't picked up by then.
It almost looks like in 74 they show the 2 hoses crossing right at the nipples. It would have been so easy to make the drawing clear!!!!!!
Thanks again!
Regards,
Alan
Thanks for the picture.
It's interesting in that it appears to be the same drawing as in my 71 AIM, but has been modified with the changes that were needed when the wiper door was dropped.
I don't understand why the problem wasn't picked up by then.
It almost looks like in 74 they show the 2 hoses crossing right at the nipples. It would have been so easy to make the drawing clear!!!!!!
Thanks again!
Regards,
Alan
Race Director
Joined: May 2006
Posts: 16,528
Likes: 53
From: Dayton, Ohio
Hi,
I, too, believe the blue hose goes on the #3 nipple..... BUT..... I've been curious about what happens if you move the nipples to the 'wrong' position AND move the blue hose to the #2 nipple.
Did the switch/nipples change at some point and that's why the AIM is wrong?
Regards,
Alan
PS: I'm really only familiar with the 71 AIM, so I'm not sure what years might be right or wrong.
I, too, believe the blue hose goes on the #3 nipple..... BUT..... I've been curious about what happens if you move the nipples to the 'wrong' position AND move the blue hose to the #2 nipple.
Did the switch/nipples change at some point and that's why the AIM is wrong?
Regards,
Alan
PS: I'm really only familiar with the 71 AIM, so I'm not sure what years might be right or wrong.
Race Director
Joined: May 2006
Posts: 16,528
Likes: 53
From: Dayton, Ohio
Maybe another approach would be to say that when any of the valves are pulled out the nipple furthest from the valve is open and "LEAKS" so you wouldn't want the supply line from the engine attached because you would have a vacuum leak.
Burning Brakes
Joined: Aug 2001
Posts: 854
Likes: 7
From: dudley ma
crf311,
glad to hear you problem is solved. I have a related question. The maintenance switch, can they go bad? My head lights work but not the main. switch. Checked and looks like hoses are in the correct locations.
Thank you
glad to hear you problem is solved. I have a related question. The maintenance switch, can they go bad? My head lights work but not the main. switch. Checked and looks like hoses are in the correct locations.
Thank you
