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Topic: Headlight doors will not open.

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Headlight doors will not open. (1/9)
 5/5/21 4:51pm
Babyblue 78
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Vette(s):
1978 Corvette Light Blue Pulled from the swamps of Miami! Its a driver and back on the road!


Joined: 12/3/2007
Posts: 274

Sorry if in the wrong place but could not find a fit for Vacuum in the other topics so I will post it here.

 

I am having a issue with the headlight doors not opening.  THe lights are all working with the headlight switch correctly and the headlights come on but the doors will not raise.

 

If I nudge the passenger side just a tad it will flip up and right away the drivers side pops up, but lately it is hit or miss if I can get one or none to open as I am driving and if so it is usually the drivers side.  Right or wrong I sprayed some silicone spray on the metal side connections and the actuator and maybe helped a tad but still will not open easily.  How do I check the vacuum and is there a step by step procedure on what should be tried first or where to search first for the answer.

 

Thanks for your responses in advance.

 

Babyblue78

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Re: Headlight doors will not open. (2/9)
 5/5/21 9:46pm
Adams' AppleLifetime Member
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Duncanville, TX - USA

Vette(s):
#1-1974 L-48 4spd Cp Med Red Metallic/Black deluxe int w/AC/tilt/tele./p/w-p/b/ Am-Fm/map light National/Regional/Chapter NCRS "Top Flight" #2-1985 Bright Red/Carmine Cp.L-98/auto Member: NCRS, NCRS Texas, Corvette Legends of Texas


Joined: 11/8/2003
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Mark, check your email. I sent you extensive troubleshooting guides for the headlight vacuum system. 🤠



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Re: Headlight doors will not open. (3/9)
 5/7/21 8:14pm
Babyblue 78
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1978 Corvette Light Blue Pulled from the swamps of Miami! Its a driver and back on the road!


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Thanks for the checklist, I got it. Will let you know what I find out when I get to it.

 

Babyblue78

Re: Headlight doors will not open. (4/9)
 5/8/21 8:03pm
F4Gary
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Grapevine, TX - USA

Vette(s):
1972 LT-1 convertible with factory air.


Joined: 8/26/2006
Posts: 1076

Get yourself a Mighty Vac hand vacuum pump.  You can test your lines and vacuum canisters.

 

https://www.harborfreight.com/mityvac-vacuum-pump-39522.html



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Re: Headlight doors will not open. (5/9)
 5/9/21 12:57pm
Babyblue 78
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1978 Corvette Light Blue Pulled from the swamps of Miami! Its a driver and back on the road!


Joined: 12/3/2007
Posts: 274

Thanks for the idea I will be getting to it real soon.

 

Thanks,

 

Babyblue78

 

Re: Headlight doors will not open. (6/9)
 9/7/21 11:50am
Babyblue 78
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1978 Corvette Light Blue Pulled from the swamps of Miami! Its a driver and back on the road!


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Posts: 274

Ok see if I can explain this. I have a copy of the Headlight trouble shooting guide (Thanks Adam's Apple). I had some time to trouble shoot so this is what I found.  I get it that the Vacuum is what closes the headlight doors, Ok.  THE ENGINE IS RUNNING ALL TESTS I pull off the 2 hoses at the checkvalve one at a time. Photo 1 and 2.I get vacuum reading of 5 psi #2 and 13psi#1 to tank. If I pull off the hose coming out of the dash (white) the doors open both fine and put hose back on the doors close.  Ok makes sense. I pull of the white hose at the T #3 and the vac is 5psi and the doors open, put the hose back on the doors close. Ok so I got good vac to the front of the engine.all hoses on pulling the light switch the lights go on/up ok no vacuum holding them down that works ok. As I have the light switch on the vacuum tank line #1 still shows 13 psi.  I'm not sure on my notes but I believe I pulled the #1 vac tank hose and the lights would not go down so that makes sense needs vac to go down.

Now I start over and pull the headlight switch and I pull the pull down switch open and I pull the white #3 hose and the lights would not go up????

 

Shou;d the white hose have more then 3-5 psi in it???

I'm thinking the other line t'd off of #2 to the wipers is maybe the problem.

 

I did have all hoses on and engine running and pulled the light switch on/off several times and it all worked ok, but trying it several times before other days it would not.

so later I go for a drive and pull the head light switch and no doors/lights up I continue to drive about another 5 minutes then they come up but once I put them down they would not come up... When I pull hoses to open doors they sort of popped open no hesitation but on the light switch it is hit or miss so I have more research to do.  I will run the whole list when I have time but I was thinking once I pulled hose#3 at the lights and it worked fine that the system was fixed some how but I guess not???

Any input would be greatly appreciated.

 

Thanks Baby Blue 78

https://www.C3VR.com/member_uploads/11101_11200/11141/C3-Vacuum-diagram20219785013r.jpg

 

Re: Headlight doors will not open. (7/9)
 9/8/21 12:44pm
JP5665
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Re: Headlight doors will not open. (8/9)
 9/8/21 2:37pm
Babyblue 78
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1978 Corvette Light Blue Pulled from the swamps of Miami! Its a driver and back on the road!


Joined: 12/3/2007
Posts: 274

Ok I will read the reply in a few. So last night I went out to the garage and started the 78 and I pulled the headlights switch out and the doors opened , both...and I turned the switch off and the doors closed.  Ok so I will just try it again before going for a ride. Well neither door opened again.  So I go for a ride and I turn the headlight switch on and leave it on and a while later the drivers side door opens but not the right one.  I turn the switch off and drive some more and then turn the light switch on and nothing until many minutes later the driver side door opens but no right side?

 

So I go home and get out pop the hood and said I'll do the two hose test I did originally and see if that still works...well nothing... Neither door opened and I tried hose at #2  and #3 which worked 2 days ago.  So now I don't know what is going on.  So I got the drivers door open and pull3ed the bypass switch and shut down the engine. I figured I would leave it that way to the morning and then shut off the light with the light switch and see if the vaccum tank held overnight.  Well nothing it would not close. I went for another ride of over 25 minutes and could not get other then once the driver door to pop open,. I will read the posted article and then run through the entire checklist and take notes but I have a feeling the light switch is the original one and time for a new one, but then that does not answer while I got it working fine the other night by pulling the hose at #3.

 

Ok thanks for your responses.

 

Babyblue 78.

Re: Headlight doors will not open. (9/9)
 9/8/21 5:56pm
F4Gary
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Grapevine, TX - USA

Vette(s):
1972 LT-1 convertible with factory air.


Joined: 8/26/2006
Posts: 1076

Have you checked to see if your vacuum tank will hold a vacuum?

Also, you might remove the white vacuum filter and just main line it to see if that affects anything.

Also take the one way check valve that right after the filter off and suck on both sides to make sure it is still a check valve.



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