C3 Headlight timing.
Thread Starter
Cruising
Joined: Jul 2016
Posts: 10
Likes: 0
From: Canada
C3 Headlight timing.
I have a 1977 Corvette and both headlights come up and are fully functional, but the right one has a very long delay and deploys very slowly. I was wondering if anyone knew how to fix this or if it was normal. Thank you
Melting Slicks
Joined: Apr 2007
Posts: 3,189
Likes: 111
From: Tolland CT
Mine pop up quite quickly, nearly simultaneous. Sounds like you may have a vacuum leak or an issue with the mechanism binding. Look over the mechanism, look for worn or broken nylon guides, missing or broken springs. I don't know whether 77 had one or two vacuum relays for the headlights. If it has two, check the relay for the slower headlight, could be leaking.
Check for leaks on the actuator.
Check for leaks on the actuator.
Team Owner
Joined: Sep 2006
Posts: 31,315
Likes: 4,418
From: Westminster Maryland
Hi Noah,
Welcome!
First post!
No, it's not normal. Both headlights should open quickly and at nearly, if not the same, time.
You might want to try reversing the hoses from the relays to the actuators (change which of the 2 actuators the relays are controlling).
If the problem remains the same you'll know the actuator is at fault (leaking), but if the other headlight light door is now the slow one you'll know it's that relay that has the problem.
You can then address the problem knowing where to start.
Good Luck!
Regards,
Alan
Move these hoses.
Welcome!
First post!
No, it's not normal. Both headlights should open quickly and at nearly, if not the same, time.
You might want to try reversing the hoses from the relays to the actuators (change which of the 2 actuators the relays are controlling).
If the problem remains the same you'll know the actuator is at fault (leaking), but if the other headlight light door is now the slow one you'll know it's that relay that has the problem.
You can then address the problem knowing where to start.
Good Luck!
Regards,
Alan
Move these hoses.
Drifting
Joined: Aug 2010
Posts: 1,839
Likes: 45
From: nassau co. new york
i resolved this problem by removing one vacuum relay and tee'ing off all the hoses to feed both actuators.not sure why 2 are necessary as mine work quick and together with a faster response.less stuff to leak also.
Safety Car
Joined: Oct 2007
Posts: 3,729
Likes: 267
From: Austin Texas
Corvette of the Year Winner 2017
2016 C3 of Year Finalist
they did it that way as a safety feature, if 1 fails, other unit still works.
When I restore a C3 I use only 1 relay valve so they both work at same time ... always.
If it ever fails I will fix it.
When I restore a C3 I use only 1 relay valve so they both work at same time ... always.
If it ever fails I will fix it.
Burning Brakes
Joined: Jul 2014
Posts: 831
Likes: 54
From: Arlington TX
Corvette Stories
The Best of Corvette for Corvette Enthusiasts
5 Best & 5 Worst Corvette Daily Drivers
Joe Kucinski
The Headlights of Every Corvette Generation Explained
Joe Kucinski
5 Best & 5 Most Overrated Corvette Track Packages of All Time!
Joe Kucinski
Every 2027 Corvette Engine Explained
Joe Kucinski
Designer Imagines A Corvette That Looks More Like a Corvette Than the Corvette
Verdad Gallardo
10 Ugly Corvettes That We Still Kinda Love
Joe Kucinski
Top 10 Most Expensive Corvettes Ever Sold on Bring A Trailer
Brett Foote
10 Things Every Corvette Owner Needs (2026 Edition)
Michael S. Palmer
8 Most "Only Corvette Owners Understand" Quirks and Problems
Pouria Savadkouei
Burning Brakes
Joined: Jul 2004
Posts: 1,194
Likes: 111
From: If your not the lead dog the view never changes Boise, Id
Can someone diagram using one vacume relay for me, I'd like to try it but having a hard time visualizing it. Thanx
Last edited by RockyL32; Aug 18, 2016 at 06:53 PM.
Team Owner
Joined: Jan 2006
Posts: 37,637
Likes: 3,118
From: Crossville TN
The Chevy engineers were 'thinking' of safety (having at least one headlamp up and working, if one side had a part failure) rather than having them "timed" the same. If you are smart, that's the same strategy you would choose, as well.
Follow Alan71's advice; then replace the vacuum relay that is worn out/malfunctioning (or both of them).
Follow Alan71's advice; then replace the vacuum relay that is worn out/malfunctioning (or both of them).
Burning Brakes
Joined: Jul 2009
Posts: 935
Likes: 20
From: Indianapolis Indiana
beFore you replace an entire line. Try this clever little trick I was shown when my vacuum system was having issues. Clip off a half inch or so of the end of the lines. A lot of time, that very end that gets stretched looses its elasticity and wont hold a vacuum. By clipping off the dried out end portion, you can often get the original hose to work quite well.
I hope that made sense.
I hope that made sense.
Racer
Joined: Jul 2009
Posts: 338
Likes: 9
From: South Bend IN
NCM Sinkhole Donor
Try pulling the headlight vacuum hose at the supply source while the engine is running and plug the leak. Does the engine idle significantly better? If so, you have a leak in your system. I did this on mine and ended up replacing hoses, relays, and actuators. I couldn't believe how much better the engine ran without a massive vacuum leak and how fast the lights come up.
Burning Brakes
Joined: Jul 2014
Posts: 831
Likes: 54
From: Arlington TX
The Chevy engineers were 'thinking' of safety (having at least one headlamp up and working, if one side had a part failure) rather than having them "timed" the same. If you are smart, that's the same strategy you would choose, as well.
Follow Alan71's advice; then replace the vacuum relay that is worn out/malfunctioning (or both of them).
Follow Alan71's advice; then replace the vacuum relay that is worn out/malfunctioning (or both of them).
I went to a single relay design after having three garbage aftermarket relays not work right out of the box on me. Make sure you test your relay when you open it.
Burning Brakes
Joined: Jul 2014
Posts: 831
Likes: 54
From: Arlington TX
My car sits mostly in my garage not being driven too
Last edited by Strokemyaxe; Aug 19, 2016 at 05:22 PM.
Drifting
Joined: Aug 2010
Posts: 1,839
Likes: 45
From: nassau co. new york
my car is actually running very well now,finally,and i am afraid to make any further improvements due to sub par replacement parts.btw i restored my original headlight relay,soaked the seals in brake fluid,and thank god i did.more parts more stuff to go wrong.