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Headlight problem

Old 10-28-2018, 07:00 PM
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Ramirez1976
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Default Headlight problem

The headlights on my 76 start to go up as soon as I start the car, the switch isn't even pulled and they go up slowly. As far as I can tell everything is hooked up correctly. I have tried pulling the override switch up and starting the car, pulling it down and starting the car, even pulling the headlight switch out with the override and they still go up. It's like no matter what I try to do to prevent them from going up, they still go up when the car starts. Anyone know what could be causing this??

-Ben
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Old 10-28-2018, 08:19 PM
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Start by testing the check valve, here's how:

http://www.corvette-101.com/vacuum.htm
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Old 10-28-2018, 09:32 PM
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Ramirez1976
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Looks like check valve is bad, just ordered a new one. Ill let y'all know if it fixes anything. Thank you.
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Old 11-03-2018, 12:44 PM
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Check valve came in the mail and I just installed it, nothing seems to have changed exept for the speed of the headlights going up. I've also got a new headlights switch cause mine was going bad but I doubt that will fix it. Any suggestions?
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Old 11-03-2018, 01:16 PM
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Default Headlight problems!

Hi again,
Just follow the instructions in the link and you'll find the problem. Click on the diagram to enlarge it.

Might not be a problem with the switch but if you change it don't mix up the hoses on the headlight switch.


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Old 11-03-2018, 09:26 PM
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Did you check to see if the manual override switch was pulled down? Or, someone might have "played" with the vacuum hoses on the override switch so it doesn't work as intended.
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Old 11-03-2018, 09:44 PM
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Originally Posted by 7T1vette View Post
Did you check to see if the manual override switch was pulled down? Or, someone might have "played" with the vacuum hoses on the override switch so it doesn't work as intended.
Ill try to test that.
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Old 11-05-2018, 07:40 PM
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You never mentioned if the headlight doors go back down after they came up when you started teh engine or not.

Do they go back down or do they stay up as long as the engine is running????

DUB
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Old 11-05-2018, 09:49 PM
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Originally Posted by DUB View Post
You never mentioned if the headlight doors go back down after they came up when you started teh engine or not.

Do they go back down or do they stay up as long as the engine is running????

DUB


If the lamps go up and then down the issue is on the small hose side. What happens is this... The small hose side has to block vacuum to hold the lamps down, the default on this system is if there is a failure in the small hose side, the lamps will raise. So... if the lamps come up and then go down when you start the car the issue is on the small hose side.

What is happening is that when the car is off the vacuum is bleeding off the small hose side and when you start the car the large hose side prevails until vacuum builds up in the system and then the small hose side kicks in and the lamps lower. So... Like mentioned above... the check valve is more than likely the culprit... If it's not checking the vacuum it'll bleed off and cause the exact issue you have assuming the doors open and then close when running.... If not post back and we'll dig deeper.

Willcox

Last edited by Willcox Corvette; 11-05-2018 at 09:50 PM.
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Old 11-09-2018, 12:49 AM
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Originally Posted by DUB View Post
You never mentioned if the headlight doors go back down after they came up when you started teh engine or not.

Do they go back down or do they stay up as long as the engine is running????

DUB
The headlights stay up when the engine is shut off, I have to manually lower them.
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Old 11-09-2018, 12:55 AM
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Originally Posted by Willcox Corvette View Post


If the lamps go up and then down the issue is on the small hose side. What happens is this... The small hose side has to block vacuum to hold the lamps down, the default on this system is if there is a failure in the small hose side, the lamps will raise. So... if the lamps come up and then go down when you start the car the issue is on the small hose side.

What is happening is that when the car is off the vacuum is bleeding off the small hose side and when you start the car the large hose side prevails until vacuum builds up in the system and then the small hose side kicks in and the lamps lower. So... Like mentioned above... the check valve is more than likely the culprit... If it's not checking the vacuum it'll bleed off and cause the exact issue you have assuming the doors open and then close when running.... If not post back and we'll dig deeper.

Willcox
Well I did replace the check valve with a brand new one but it did not make a difference, the lamps still go up when I start the engine and do not go down when it is shut off
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Old 11-09-2018, 10:47 AM
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SO if your headlight doors are coming up when you start the engine and they stay up the entire time while the engine is running and NEVER go back down. And your are 100% positive you have the hoses routed CORRECTLY. The I say you have a problem with the vacuum in the small hose going to the actuator relays staying off or very low thus causing the headlight doors to go to the default setting adn raise when there is little to no vacuum on this small hose.

When the engine is running and the headlight and override switch are OFF...the vacuum on that small hose needs to be a lot to allow it to pull the valve in it to keep the headlight doors down. Simple as that.

DUB
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Old 11-09-2018, 10:53 AM
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Granted it also depends of your vacuum storage tank is good so even with new check valve....if the vacuum storage tank can not hold vacuum...you headlight will do this until it is corrected. But even with that....you will be able to detect this issue due to lack of good vacuum on the small hose.

You can...if you want to.....take a long section of vacuum hopes and connect it to your actuator relays and THEN remove the small hose off of your new check valve and attach it there This is by passing all of your interiors switching for the headlights.

IF you crank the engine and the headlight doors still go up and stay.... I then would look at IF you vacuum storage tank is any good.by using a vacuum gauge.

DUB
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Old 11-09-2018, 11:15 AM
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What you could do with the car running pull the small hose off the vacuum relay at the headlamps. See if you have vacuum on that hose. In the schematic below that would be M and N connections. If you have vacuum there with the car running then you should test the relay's.

If you don't have vacuum there the keep backing up the hose and testing at the different connections such as L A H and AA

There is a ton of info on your system at this link: http://repairs.willcoxcorvette.com/?yt=1976&s=headlamp

Vacuum hose schematic.


How the rely works


1968-1982 Corvette Headlamp Vacuum Diagnostic Help.


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Old 11-09-2018, 11:51 PM
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👍 Willcox
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Old 11-14-2018, 03:54 PM
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Ramirez1976
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Thanks for all the help, I've been sick for the past week or so, I'll get to it when I can and let y'all know what happens.
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