Headlights won't stay down
Thread Starter
Instructor
Joined: Jan 2015
Posts: 200
Likes: 15
From: shreveport Louisiana
Headlights won't stay down
I want to go for a ride but every time I start the car the headlights pop up and it bothers the crap out of me. Now I know I need to fix the problem but is there a simple way to plug a hose and manually close the headlights until I can fix it so I'm not riding around with them up all the time
Le Mans Master
Joined: Aug 2006
Posts: 7,427
Likes: 1,560
From: mount holly NC
2025 c3 ('74-'82) of the Year Finalist - Unmodified
2019 C3 of Year Finalist (appearance mods)
Hi Danny,
Make sure that the 'pull down' switch is in the correct position.
If that does not work locate the white plastic filter, disconnect it and plug the rubber hose going to the intake manifold.
http://www.corvette-101.com/vacuum.htm#override
Make sure that the 'pull down' switch is in the correct position.
If that does not work locate the white plastic filter, disconnect it and plug the rubber hose going to the intake manifold.
http://www.corvette-101.com/vacuum.htm#override
Le Mans Master
Joined: Jul 2006
Posts: 8,117
Likes: 104
From: charlotte north carolina
The system is designed so that a low(or none) vacuum signal to the relay will open the headlights. That's a safety measure so that in case of a component failure the driver will still have headlights. Check the control hose on the relay for a good vacuum. More that likely the relay is bad-a common issue.
Drifting
Joined: Oct 2005
Posts: 1,615
Likes: 150
From: Forth Worth TX
The system is designed so that a low(or none) vacuum signal to the relay will open the headlights. That's a safety measure so that in case of a component failure the driver will still have headlights. Check the control hose on the relay for a good vacuum. More that likely the relay is bad-a common issue.
If the headlight buckets are up and you lose all vacuum, they remain up. If the headlight buckets are down and you lose all vacuum they remain down.There is no "safety measure" to make them pop-up for any reason. The "override pull down switch" is to raise the headlight buckets without electricity going to the lights so you can change a bulb.
If the vacuum system is inoperative, you simply reach under the front of the car and you can manually manipulate the headlight buckets either up or down as necessary.
Last edited by Revi; May 12, 2016 at 07:55 PM.
Dr. Detroit
Joined: Mar 2012
Posts: 10,097
Likes: 4,027
From: New Braunfels Texas
That's not how the system works. Vacuum is used to either open or close the headlight buckets. It is used as muscle to move the headlights up and over center on their hinges or move them closed and over center on their hinges. The "over center" part of the hinges/springs is what keeps them in place.
If the headlights buckets are up and you lose all vacuum, they remain up. If the headlight buckets are down and you lose all vacuum they remain down.There is no "safety measure" to make them pop-up for any reason.
If the vacuum system is inoperative, you simply reach under the front of the car and you can manually manipulate the headlight buckets either up or down as necessary.
If the headlights buckets are up and you lose all vacuum, they remain up. If the headlight buckets are down and you lose all vacuum they remain down.There is no "safety measure" to make them pop-up for any reason.
If the vacuum system is inoperative, you simply reach under the front of the car and you can manually manipulate the headlight buckets either up or down as necessary.
The relay activator has vacuum to it all of the time.....when this vacuum is cut...the headlight will pop up.....
Pull the small hose on the top of the relay and you will see this.....it is how you test the relays BTW....as well as other parts of the system.
The large hose that makes the lights go up and down goes to the center of the relay...from there the relay cuts one or the other depending on position. Up or Down.
Consequently....check your headlight switch and the lines coming to and from it as well as the override under the column...it can leak there too.....
Jebby
Last edited by Jebbysan; May 12, 2016 at 07:57 PM.
Drifting
Joined: Oct 2005
Posts: 1,615
Likes: 150
From: Forth Worth TX
Go out to your car, start it, with it at idle, disconnect the vacuum hose from the intake manifold to the vacuum tank. Do your headlights pop up? They shouldn't.
Last edited by Revi; May 12, 2016 at 08:36 PM.
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Dr. Detroit
Joined: Mar 2012
Posts: 10,097
Likes: 4,027
From: New Braunfels Texas
If lose vacuum to the small hoses on top of the relay and not from the canister....the headlights WILL go up....end of story.
Jebby
Dr. Detroit
Joined: Mar 2012
Posts: 10,097
Likes: 4,027
From: New Braunfels Texas
You all need to go through the schematic and learn how they operate.
The actuator through the headlight switch is completely separate from the vacuum canister.
From the headlight switch...vacuum is supplied all of the time.
If you lose this vacuum....the headlights will lift....assuming you have not lost vacuum from the canister....
Please...will somebody else come in and explain this?
I know what I know and diagnosed two of these systems in the last few months....
When you pull the headlight switch....it cuts vacuum to the diaphragm at the relay....the plunger inside drops and the headlights rise. Period. Pulling the lines from the relay will do the exact same thing.
Of course the vehicle must be running to do this....
How do you think the headlights are triggered to go up and down?
Jebby
Last edited by Jebbysan; May 12, 2016 at 09:05 PM.
Drifting
Joined: Oct 2005
Posts: 1,615
Likes: 150
From: Forth Worth TX
I am sorry...but they will...they lift.
You all need to go through the schematic and learn how they operate.
The actuator through the headlight switch is completely separate from the vacuum canister.
From the headlight switch...vacuum is supplied all of the time.
If you lose this vacuum....the headlights will lift....assuming you have not lost vacuum from the canister....
Please...will somebody else come in and explain this?
I know what I know and diagnosed two of these systems in the last few months....
When you pull the headlight switch....it cuts vacuum to the diaphragm at the relay....the plunger inside drops and the headlights rise. Period. Pulling the lines from the relay will do the exact same thing.
Of course the vehicle must be running to do this....
How do you think the headlights are triggered to go up and down?
Jebby
You all need to go through the schematic and learn how they operate.
The actuator through the headlight switch is completely separate from the vacuum canister.
From the headlight switch...vacuum is supplied all of the time.
If you lose this vacuum....the headlights will lift....assuming you have not lost vacuum from the canister....
Please...will somebody else come in and explain this?
I know what I know and diagnosed two of these systems in the last few months....
When you pull the headlight switch....it cuts vacuum to the diaphragm at the relay....the plunger inside drops and the headlights rise. Period. Pulling the lines from the relay will do the exact same thing.
Of course the vehicle must be running to do this....
How do you think the headlights are triggered to go up and down?
Jebby
Apply vacuum to one side of the actuator and the headlights pop-up. Once the headlights are up, it's the over-center of the spring hinge that holds them up. While vacuum may still be applied to the up side of the actuator it isn't actually holding the buckets up. If you lose vacuum, the headlights will remain up.
The same holds true with lowering the headlights. You're just applying vacuum to the other side of the same actuator to move them over center to close.
This one particular failure that you are describing as "raising the headlights" is basically mimicking turning the headlights on. It's not a "safety feature" to raise the headlights. Other vacuum failures within the system will not move the headlight buckets.
It's like saying a shorted out wiring harness which happens to turn the headlight bulbs on all of the time is some type of safety feature.
Last edited by Revi; May 12, 2016 at 09:22 PM.
Dr. Detroit
Joined: Mar 2012
Posts: 10,097
Likes: 4,027
From: New Braunfels Texas
Vacuum is used/supplied to both sides of the actuator (one side at a time) depending on what you ask of it.
Apply vacuum to one side of the actuator and the headlights pop-up. Once the headlights are up, it's the over-center of the spring hinge that holds them up. While vacuum may still be applied to the up side of the actuator it isn't actually holding the buckets up. If you lose vacuum, the headlights will remain up.
The same holds true with lowering the headlights. You're just applying vacuum to the other side of the same actuator to move them over center to close.
This one particular failure that you are describing as "raising the headlights" is basically mimicking turning the headlights on. It's not a "safety feature" to raise the headlights. Other vacuum failures within the system will not move the headlight buckets.
It's like saying a shorted out wiring harness which happens to turn the headlight bulbs on all of the time is some type of safety feature.
Apply vacuum to one side of the actuator and the headlights pop-up. Once the headlights are up, it's the over-center of the spring hinge that holds them up. While vacuum may still be applied to the up side of the actuator it isn't actually holding the buckets up. If you lose vacuum, the headlights will remain up.
The same holds true with lowering the headlights. You're just applying vacuum to the other side of the same actuator to move them over center to close.
This one particular failure that you are describing as "raising the headlights" is basically mimicking turning the headlights on. It's not a "safety feature" to raise the headlights. Other vacuum failures within the system will not move the headlight buckets.
It's like saying a shorted out wiring harness which happens to turn the headlight bulbs on all of the time is some type of safety feature.
The relays send the appropriate vacuum (which is supplied to the center port...from the reservoir canister) to the front or rear side of the pie pan.
The relay has a plunger in it that lets vacuum to the upper vacuum line off the relay or the lower. This is controlled by the diaphragm up top. This diaphragm has its own separate line that runs inside the car, to the override switch, through the headlight switch and outside the firewall to the intake manifold. The smaller line is 100% separate from the vacuum lines that actually make the lights go up and down.
This smaller line is the "control" for the relay. If you cut vacuum to it...which is what happens when you pull the headlight switch....and assuming the car is running and the system works properly....the headlights lift. Push the switch in and it restores vacuum to the relay...which pulls the plunger in the relay up....allowing vacuum to the opposite side of the pie pan and the headlight shuts.
The "control" and "muscle" vacuum circuits are 100% separate.
Study this diagram and you will see....
Jebby
Le Mans Master
Joined: Aug 2006
Posts: 7,427
Likes: 1,560
From: mount holly NC
2025 c3 ('74-'82) of the Year Finalist - Unmodified
2019 C3 of Year Finalist (appearance mods)
Everybody is correct!
Hi Jebbysan,
You are correct that if you disconnect the small rubber line at the check valve, or pull the headlight switch out or use the pull-down switch the headlights will pop up.
The reason for that is because the spring in the relay pushes the 'dog-bone' in the relay down which sends vacuum to the (yellow) center port of the relay which makes the lights go up.
Hi Revi,
You are also correct that there is no default position. If you loose vacuum the lights stay up or down.
Most times when the lights won't go up it's because the seal in the actuator(S) is leaking.
The OP asked for a temporary fix to keep his headlights down so I suggested disconnecting the vacuum at the source, which is the first rubber hose coming from the manifold. He can now go under the front and close the headlights and they will stay down.
Glad no one asked about a wiper door. LOL!
You are correct that if you disconnect the small rubber line at the check valve, or pull the headlight switch out or use the pull-down switch the headlights will pop up.
The reason for that is because the spring in the relay pushes the 'dog-bone' in the relay down which sends vacuum to the (yellow) center port of the relay which makes the lights go up.
Hi Revi,
You are also correct that there is no default position. If you loose vacuum the lights stay up or down.
Most times when the lights won't go up it's because the seal in the actuator(S) is leaking.
The OP asked for a temporary fix to keep his headlights down so I suggested disconnecting the vacuum at the source, which is the first rubber hose coming from the manifold. He can now go under the front and close the headlights and they will stay down.
Glad no one asked about a wiper door. LOL!
Thread Starter
Instructor
Joined: Jan 2015
Posts: 200
Likes: 15
From: shreveport Louisiana
Well I figured it out. I was going to plug it were Pete said and when I was looking around there was a hose disconnected at the check valve and everything works great now
