Droopy Headlight Help
Thread Starter
Intermediate
Joined: Sep 2015
Posts: 25
Likes: 0
Droopy Headlight Help
Hello all-
Bought my first vette yesterday! '79 L48. Weird issue with the headlights though. Here it is, and if There's a sticky on this already please let me know.
Start engine. Allow her to 'settle' takes about 2 mins from a cold start. Pull the headlight switch. Right goes up with no trouble at all. Left comes up about a half inch. Push the headlight switch in. Pull down the manual override. Left comes up no problem, right comes up just a little.
I've looked at several diagrams in the forum here and am kind of at a loss as to what could cause this. Any thoughts would be much appreciated! Thanks!
Bought my first vette yesterday! '79 L48. Weird issue with the headlights though. Here it is, and if There's a sticky on this already please let me know.
Start engine. Allow her to 'settle' takes about 2 mins from a cold start. Pull the headlight switch. Right goes up with no trouble at all. Left comes up about a half inch. Push the headlight switch in. Pull down the manual override. Left comes up no problem, right comes up just a little.
I've looked at several diagrams in the forum here and am kind of at a loss as to what could cause this. Any thoughts would be much appreciated! Thanks!
Team Owner
Joined: Sep 2006
Posts: 31,301
Likes: 4,390
From: Westminster Maryland
Hi D,
New, old Corvette!!!
Good for you!
There should be enough vacuum to operate the headlights as soon as the engine is running.
The headlight switch directs a vacuum signal to two small 'relays' mounted in the front of the car. The relays then send a vacuum signal to each of the headlight actuators.
You can check the function and operation of the relays, and the 'open/close' seals and diaphragm in the actuators with a vacuum pump with a gauge.. like a mity-vac.
Have you used the diagrams to verify that the parts and hoses are all routed properly and securely on the relay and actuator pipes? Should be small diameter hoses for the 'control' part of the system and large diameter hose for 'servo' side.
Regards,
Alan
How about a few photos of your new car?
New, old Corvette!!!
Good for you!
There should be enough vacuum to operate the headlights as soon as the engine is running.
The headlight switch directs a vacuum signal to two small 'relays' mounted in the front of the car. The relays then send a vacuum signal to each of the headlight actuators.
You can check the function and operation of the relays, and the 'open/close' seals and diaphragm in the actuators with a vacuum pump with a gauge.. like a mity-vac.
Have you used the diagrams to verify that the parts and hoses are all routed properly and securely on the relay and actuator pipes? Should be small diameter hoses for the 'control' part of the system and large diameter hose for 'servo' side.
Regards,
Alan
How about a few photos of your new car?
Last edited by Alan 71; Mar 5, 2017 at 12:10 PM.
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)
Hi and welcome.
Many times the seal (grommet) in the actuator needs to be replaced.
Here's a troubleshooting guide to help you find and fix the problem.
http://www.corvette-101.com/vacuum.htm
Here's a troubleshooting guide to help you find and fix the problem.
http://www.corvette-101.com/vacuum.htm
Melting Slicks
Joined: May 2015
Posts: 2,365
Likes: 428
From: Cape Girardeau Missouri
Welcome and congratulations!
You'll find there are LOTS of vacuum hoses in a '79.
Perhaps the best tool purchase you can make is a Mity Vac (or similar) hand vacuum pump. They are inexpensive and you can get them at any auto parts store.
With a little searching you can find excellent instructions for troubleshooting the vacuum headlamp units and the components therein. As long has you have the hand vacuum pump (the electrical vacuum pumps like used for A/C are too powerful) it shouldn't take long for you to identify the problem(s).
Your "start engine wait a couple minutes to 'settle down'" comment reminds me a bit of my '79 when it was new to me. I now attribute that mainly to vacuum leaks--non severe-but essentially at every hose connection. The only vacuum system that didn't leak was for HVAC. HVAC uses a different concept--small hard plastic tubes with soft rubberized boots at connections.
Old hoses stretch out at the ends and even if the hose tests perfectly it may leak when installed. Some hoses have enough length that you can cut off an inch or two at each end-that should stop the leak for a while--but since the hoses are old and loosing elasticity it's best to replace them.
Do a search for Doc Rebuild. He sells excellent quality cut-to-length and striped-as-original kits with excellent installation diagrams for every vacuum operated system in our cars.
You'll find this forum invaluable when enjoying your new toy. "Enjoying" our cars typically involves quite a bit of diagnosis, wrench turning and, at times, significant frustration. Be patient! The OEM parts are of quite good quality and last surprisingly long but interior plastics can get somewhat brittle. You can get replacement parts for most anything but the Corvette specific aftermarket parts are generally inferior to OEM. Always try to save your original parts and if you do decide to replace consider putting them for sale here as a great many member value them highly enough to spend considerable time repairing them.
You'll find there are LOTS of vacuum hoses in a '79.
Perhaps the best tool purchase you can make is a Mity Vac (or similar) hand vacuum pump. They are inexpensive and you can get them at any auto parts store.
With a little searching you can find excellent instructions for troubleshooting the vacuum headlamp units and the components therein. As long has you have the hand vacuum pump (the electrical vacuum pumps like used for A/C are too powerful) it shouldn't take long for you to identify the problem(s).
Your "start engine wait a couple minutes to 'settle down'" comment reminds me a bit of my '79 when it was new to me. I now attribute that mainly to vacuum leaks--non severe-but essentially at every hose connection. The only vacuum system that didn't leak was for HVAC. HVAC uses a different concept--small hard plastic tubes with soft rubberized boots at connections.
Old hoses stretch out at the ends and even if the hose tests perfectly it may leak when installed. Some hoses have enough length that you can cut off an inch or two at each end-that should stop the leak for a while--but since the hoses are old and loosing elasticity it's best to replace them.
Do a search for Doc Rebuild. He sells excellent quality cut-to-length and striped-as-original kits with excellent installation diagrams for every vacuum operated system in our cars.
You'll find this forum invaluable when enjoying your new toy. "Enjoying" our cars typically involves quite a bit of diagnosis, wrench turning and, at times, significant frustration. Be patient! The OEM parts are of quite good quality and last surprisingly long but interior plastics can get somewhat brittle. You can get replacement parts for most anything but the Corvette specific aftermarket parts are generally inferior to OEM. Always try to save your original parts and if you do decide to replace consider putting them for sale here as a great many member value them highly enough to spend considerable time repairing them.
