1981 Headlights won't come up when on
Thread Starter
7th Gear
Joined: Dec 2015
Posts: 7
Likes: 0
From: McKinney, Texas
1981 Headlights won't come up when on
Hey y'all, Brand new to the forum!
I have a question concerning the 1981 headlights. The lights won't go up unless I physically push them up. Then when I switch the lights off, they both go down normally.
So far I've replaced the filter, check valve, override switch and headlamp switch. I've traced all the lines to the headlamps and all the hoses appear to be in great shape. What I don't get it the absence of vacuum causes the lights to go up and the presence of vacuum causes them to go down.
The light go down perfectly. They don't rise and that's the problem.
How often does a vacuum tank go bad too?
What are some suggestions?
I have a question concerning the 1981 headlights. The lights won't go up unless I physically push them up. Then when I switch the lights off, they both go down normally.
So far I've replaced the filter, check valve, override switch and headlamp switch. I've traced all the lines to the headlamps and all the hoses appear to be in great shape. What I don't get it the absence of vacuum causes the lights to go up and the presence of vacuum causes them to go down.
The light go down perfectly. They don't rise and that's the problem.
How often does a vacuum tank go bad too?
What are some suggestions?
Former Vendor
Joined: Aug 2006
Posts: 76,656
Likes: 1,853
From: Jeffersonville Indiana 812-288-7103
St. Jude Donor '08-'09-'10-'11-'12-'13-'14-'15
First are you sure you have the hoses on the switch in the right position.
The input hose from the engine check valve us supposed to be on the rear nipple of the headlamp switch.
So in the closed position you should have vacuum on the 8 connection at the by-pass valve. You should also have vacuum on the black with a white stripped hose all the way to the relays. (connection A or shown as Hose's 1 and 2 below.
If you have vacuum at the points mentioned... go pull the headlamp switch and see if it's drops off.
If it does then I'd look at the relay's or actuators as the issue.
If it doesn't then I would go to the over-ride and pull it downward. This should also make the headlamps rise and should stop the vacuum on the same hoses above (no vacuum at connection A or shown as hoses 1 and 2 below). If it doesn't then you probably have the hoses inverted at the headlamp switch.
Always keep in mind it takes vacuum on the small black/white stripped hose to hold the lamps down, and lack of vacuum on that same hose to make them raise.
I would look for a hose issue first since you replaced all the items mentioned.
Then.. I'd start testing the relay's and the actuators. The vacuum can's on the 1980-1982 are a poor design and the reproductions are even worse. I've had to epoxy the top check valve in the repro's in the past to keep them from leaking. The current production vacuum can does't seem to be all that bad.
The input hose from the engine check valve us supposed to be on the rear nipple of the headlamp switch.
So in the closed position you should have vacuum on the 8 connection at the by-pass valve. You should also have vacuum on the black with a white stripped hose all the way to the relays. (connection A or shown as Hose's 1 and 2 below.
If you have vacuum at the points mentioned... go pull the headlamp switch and see if it's drops off.
If it does then I'd look at the relay's or actuators as the issue.
If it doesn't then I would go to the over-ride and pull it downward. This should also make the headlamps rise and should stop the vacuum on the same hoses above (no vacuum at connection A or shown as hoses 1 and 2 below). If it doesn't then you probably have the hoses inverted at the headlamp switch.
Always keep in mind it takes vacuum on the small black/white stripped hose to hold the lamps down, and lack of vacuum on that same hose to make them raise.
I would look for a hose issue first since you replaced all the items mentioned.
Then.. I'd start testing the relay's and the actuators. The vacuum can's on the 1980-1982 are a poor design and the reproductions are even worse. I've had to epoxy the top check valve in the repro's in the past to keep them from leaking. The current production vacuum can does't seem to be all that bad.
Thread Starter
7th Gear
Joined: Dec 2015
Posts: 7
Likes: 0
From: McKinney, Texas
First are you sure you have the hoses on the switch in the right position.
The input hose from the engine check valve us supposed to be on the rear nipple of the headlamp switch.
So in the closed position you should have vacuum on the 8 connection at the by-pass valve. You should also have vacuum on the black with a white stripped hose all the way to the relays. (connection A or shown as Hose's 1 and 2 below.
If you have vacuum at the points mentioned... go pull the headlamp switch and see if it's drops off.
If it does then I'd look at the relay's or actuators as the issue.
If it doesn't then I would go to the over-ride and pull it downward. This should also make the headlamps rise and should stop the vacuum on the same hoses above (no vacuum at connection A or shown as hoses 1 and 2 below). If it doesn't then you probably have the hoses inverted at the headlamp switch.
Always keep in mind it takes vacuum on the small black/white stripped hose to hold the lamps down, and lack of vacuum on that same hose to make them raise.
I would look for a hose issue first since you replaced all the items mentioned.
Then.. I'd start testing the relay's and the actuators. The vacuum can's on the 1980-1982 are a poor design and the reproductions are even worse. I've had to epoxy the top check valve in the repro's in the past to keep them from leaking. The current production vacuum can does't seem to be all that bad.
The input hose from the engine check valve us supposed to be on the rear nipple of the headlamp switch.
So in the closed position you should have vacuum on the 8 connection at the by-pass valve. You should also have vacuum on the black with a white stripped hose all the way to the relays. (connection A or shown as Hose's 1 and 2 below.
If you have vacuum at the points mentioned... go pull the headlamp switch and see if it's drops off.
If it does then I'd look at the relay's or actuators as the issue.
If it doesn't then I would go to the over-ride and pull it downward. This should also make the headlamps rise and should stop the vacuum on the same hoses above (no vacuum at connection A or shown as hoses 1 and 2 below). If it doesn't then you probably have the hoses inverted at the headlamp switch.
Always keep in mind it takes vacuum on the small black/white stripped hose to hold the lamps down, and lack of vacuum on that same hose to make them raise.
I would look for a hose issue first since you replaced all the items mentioned.
Then.. I'd start testing the relay's and the actuators. The vacuum can's on the 1980-1982 are a poor design and the reproductions are even worse. I've had to epoxy the top check valve in the repro's in the past to keep them from leaking. The current production vacuum can does't seem to be all that bad.
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)
Former Vendor
Joined: Aug 2006
Posts: 76,656
Likes: 1,853
From: Jeffersonville Indiana 812-288-7103
St. Jude Donor '08-'09-'10-'11-'12-'13-'14-'15
Use the diagram above I posted.. If you have a Mityvac pull vacuum from the rear nipple. If it will hold vacuum on the back side that's a good thing. Then move to the front side and test again.
If it leaks from the back side the diaphragm is leaking and you need an actuator.
If it leaks from the front side and hold vacuum on the backside then you need to replace the rod seal and boot.
I can not make a better point that it is always better to repair an original actuator than to replace it with the imported reproduction.
-Willcox
Last edited by Willcox Corvette; Feb 16, 2016 at 10:23 PM.
Thread Starter
7th Gear
Joined: Dec 2015
Posts: 7
Likes: 0
From: McKinney, Texas
I'm with Pete- You need to test the actuators.
Use the diagram above I posted.. If you have a Mityvac pull vacuum from the rear nipple. If it will hold vacuum on the back side that's a good thing. Then move to the front side and test again.
If it leaks from the back side the diaphragm is leaking and you need an actuator.
If it leaks from the front side and hold vacuum on the backside then you need to replace the rod seal and boot.
I can not make a better point that it is always better to repair an original actuator than to replace it with the imported reproduction.
-Willcox
Use the diagram above I posted.. If you have a Mityvac pull vacuum from the rear nipple. If it will hold vacuum on the back side that's a good thing. Then move to the front side and test again.
If it leaks from the back side the diaphragm is leaking and you need an actuator.
If it leaks from the front side and hold vacuum on the backside then you need to replace the rod seal and boot.
I can not make a better point that it is always better to repair an original actuator than to replace it with the imported reproduction.
-Willcox
Do you guys know that most of your C3 repair videos on your website show the same video, though they are labeled differently? They're all for replacing some hinge.
Anyway, I found a broken valve on the passenger side relay.
Can I buy the seal kits from wilcox?
