Headlight Actuator or Relay Valve?
Thread Starter
Cruising
Joined: Nov 2016
Posts: 13
Likes: 1
Headlight Actuator or Relay Valve?
My son has a 1980 C3. Both headlights will go down but won't come up. This problem happened suddenly. Seems odd that both actuators would go out at the same time but what do I know?
Le Mans Master
Joined: Sep 2002
Posts: 5,236
Likes: 898
From: Myrtle Beach SC
Now those headlights "pop" when I pull the light switch. Let's face it that 1980 is 38 years old. It's actually a fun project and there are restorers who will rebuild your actuators which will preserve the actuator markings, date code, etc.
But I agree, it is unusual that both actuators fail simultaneously and makes it sound like a vacuum/hose problem. That's why the troubleshooting starts with the vacuum/hose system before checking the actuators and relay.
There use to be a great troubleshooting guide posted as a sticky. Look for it as you wade into solving the 80's problem.
Hope this helps!
Team Owner
Joined: Sep 2006
Posts: 31,315
Likes: 4,418
From: Westminster Maryland
Hi H,
Since your 1980 headlight system has 2 relays and 2 actuators it's seems unlikely that both relays or both actuators would fail at the same time.
So... a control issue (small hoses) to the relays.
A wiper switch problem?
Do you hear anything when you pull the headlight switch.... a 'hiss'?
Iceaxe's question... does the override switch below the steering column open the headlight doors when it's pulled?
What are you doing to open the doors?
Regards,
Alan
Since your 1980 headlight system has 2 relays and 2 actuators it's seems unlikely that both relays or both actuators would fail at the same time.
So... a control issue (small hoses) to the relays.
A wiper switch problem?
Do you hear anything when you pull the headlight switch.... a 'hiss'?
Iceaxe's question... does the override switch below the steering column open the headlight doors when it's pulled?
What are you doing to open the doors?
Regards,
Alan
Drifting
Joined: Jul 2006
Posts: 1,259
Likes: 154
From: Deplorableville Nebraska
This problem does sound somewhat far fetched, but actually can be fairly common under some scenarios.
We know the rear seals of the actuators are good as the doors will go down. We know the control hose plumbing to and from the relays are probably good as the internal relay piston must be raised to switch the vacuum signal to the "headlight down" position.
So what can cause the "headlight up" to suddenly fail? Both relays must get the actuating vacuum from the same shared vacuum reservoir. Any massive vacuum leak from one side could also bleed vacuum through it from the other side. Consequently neither headlight door would open.
I would look for a disconnected vacuum hose at the front of the actuators and/or the bottom hose on the relays. Next check the front seals on the actuators. A quick and easy way to do this is to pinch closed the vacuum hose going to the front of each actuator one at a time. If one side has a seal leak, and the other doesn't, that one should pop up.
Here's a link to the forum headlight vacuum tutorial;
https://www.corvetteforum.com/forums...tem-works.html
We know the rear seals of the actuators are good as the doors will go down. We know the control hose plumbing to and from the relays are probably good as the internal relay piston must be raised to switch the vacuum signal to the "headlight down" position.
So what can cause the "headlight up" to suddenly fail? Both relays must get the actuating vacuum from the same shared vacuum reservoir. Any massive vacuum leak from one side could also bleed vacuum through it from the other side. Consequently neither headlight door would open.
I would look for a disconnected vacuum hose at the front of the actuators and/or the bottom hose on the relays. Next check the front seals on the actuators. A quick and easy way to do this is to pinch closed the vacuum hose going to the front of each actuator one at a time. If one side has a seal leak, and the other doesn't, that one should pop up.
Here's a link to the forum headlight vacuum tutorial;
https://www.corvetteforum.com/forums...tem-works.html
Racer
Joined: Jul 2008
Posts: 353
Likes: 30
From: warwick rhode island
it is strange that both would fail at once if there are two relays, but my vote is for relay failure. vacuum to the relays closes the headlights, but the spring in the top of the relays should open them.
of course this time if year it could be ice freezing the system.
of course this time if year it could be ice freezing the system.
Le Mans Master
Joined: Aug 2006
Posts: 7,431
Likes: 1,561
From: mount holly NC
2025 c3 ('74-'82) of the Year Finalist - Unmodified
2019 C3 of Year Finalist (appearance mods)
That other post is mostly about theory,
Here's a hands-on how to:
http://www.corvette-101.com/vacuum.htm
Here's a hands-on how to:
http://www.corvette-101.com/vacuum.htm
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