Headlights
Thread Starter
Instructor
Joined: Mar 2007
Posts: 169
Likes: 0
From: Tullahoma Tennessee
Headlights
I've got nothing, the lights won't go down when i manually pull them up, they won't come up when I turn them on. I think vaccum is supposed to keep the lights down right? I'm sure people get tired of explaining to us noobs how to correctly hook up the headlights but my system seems to be hooked up correctly and still I get nothing. 
Here's the schematic I used to connect vacuum lines.[IMG]
[/IMG]
I'm afraid it's a question of what to replace first...
Here's the schematic I used to connect vacuum lines.[IMG][/IMG]
I'm afraid it's a question of what to replace first...
Team Owner
Joined: Aug 2006
Posts: 24,125
Likes: 15
From: Columbia Missouri
Before you start replacing expensive parts you need to check your vacuum system for leaks. You can get a vacuum gun at Autozone for under $30, and use it at various points in your vacuum system to check for leaks. You can also use this gun to manually raise and lower your headlights. This will help you decide if your headlight relays and actuators are functioning properly.
Intermediate
Joined: Dec 2005
Posts: 32
Likes: 1
From: Lunenburg MA
First check to make sure that all of the lines are good. Its very possible that one of the old vaccum lines could have been severed or pinched somewhere. I just recently found a line that went to the headlight switch under the dash that was broke in my car. I also had to replace one of the relays as well to get the headlights to work right. Also you could try to just listen to the differnt parts of the system with the car running, the problem might be obvious if you can hear where the vaccum leak is comming from.
Last edited by J.Aro75Vette; Apr 23, 2007 at 09:54 PM.
Thread Starter
Instructor
Joined: Mar 2007
Posts: 169
Likes: 0
From: Tullahoma Tennessee
Sorry guys, I didn't mean replacing the entire headlight assemblies or anything. At most I'll get a vaccuum hose kit from Corvette Central. (I think some of those huge vaccum lines near the front are dry rotting) I just wanted to make sure that the diagram had the correct information for my year (1977).
Intermediate
Joined: Dec 2005
Posts: 32
Likes: 1
From: Lunenburg MA
The diagram looks correct, it just dosent show the vaccum resivor tank in the front that your 77 has. make sure the lines that are shown going into the front bumper of the car in your diagram are going to that tank. If you get your headlights start to go up but slowly, you can assume that the wiring is right but you have a small leak somewhere. Because your lights dont work at all you most likely dont have it wired right or you have a large leak like a hose off. I hope this helps.
Racer
Joined: Jan 2007
Posts: 325
Likes: 0
From: Ocala FL
Rab16
Don't spend ANY money yet unless you buy a vacuum gage or a handheld vacuum pump, like a brake bleeder or a mightyvac. All the components of the headlight system are old and EXPENSIVE, so troubleshoot first. Ask questions, get answers, then buy parts.
Do a search on my posts, I've written a lot about the headlight system in the past few weeks
Here's a link to a VERY good troubleshooting guide http://www.corvette-101.com/vacuum.htm
Don't spend ANY money yet unless you buy a vacuum gage or a handheld vacuum pump, like a brake bleeder or a mightyvac. All the components of the headlight system are old and EXPENSIVE, so troubleshoot first. Ask questions, get answers, then buy parts.
Do a search on my posts, I've written a lot about the headlight system in the past few weeks
Here's a link to a VERY good troubleshooting guide http://www.corvette-101.com/vacuum.htm
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Melting Slicks
Joined: Mar 2002
Posts: 2,140
Likes: 7
From: Ohio
I think new hoses is a waste of money unless you want them to look new. If you belive the vendors they love to sell hoses but I doubt they fix the problem 1% of the time. All the parts of the system I have found to be the soruce of the leak and never have I needed a hose kit. I have replaced a hose or two fixing about 20 sharks headlight systems.
Racer
Joined: Mar 2006
Posts: 366
Likes: 1
From: Houston Texas
There are two vacuum circuits - one makes things move, and one passes the signal when to move. If the circuit that makes things move has no vacuum, the lights will stay in whatever position you manually put them in. If this circuit works but the control circuit is dead, the lights will always open (assuming everything else is working correctly).
Easiest way to see if you have some vacuum to move things is to pull a hose coming out of the resevoir while the engine is running and see if there is some vacuum there. If yes, it is probably not the hoses that are bad, but a relay or actuator.
Hooking a hand pump to an accuator is a good way to test it is working.
Easiest way to see if you have some vacuum to move things is to pull a hose coming out of the resevoir while the engine is running and see if there is some vacuum there. If yes, it is probably not the hoses that are bad, but a relay or actuator.
Hooking a hand pump to an accuator is a good way to test it is working.
Thread Starter
Instructor
Joined: Mar 2007
Posts: 169
Likes: 0
From: Tullahoma Tennessee
Don't spend ANY money yet unless you buy a vacuum gage or a handheld vacuum pump, like a brake bleeder or a mightyvac
There are two vacuum circuits - one makes things move, and one passes the signal when to move. If the circuit that makes things move has no vacuum, the lights will stay in whatever position you manually put them in. If this circuit works but the control circuit is dead, the lights will always open (assuming everything else is working correctly).
Racer
Joined: Jan 2007
Posts: 325
Likes: 0
From: Ocala FL
Will a brake bleeder work for this application? If it will that would be great as I need to bleed my brakes anyway.
A brake bleeder works great. You can test each element to see if it maintains vacuum
It sounds like the circuit that makes things move is my problem. Thanks for the advice everybody, keep em coming.
A brake bleeder works great. You can test each element to see if it maintains vacuum
It sounds like the circuit that makes things move is my problem. Thanks for the advice everybody, keep em coming.
http://www.corvette-101.com/vacuum.htm
Instructor
Joined: May 2006
Posts: 223
Likes: 1
From: Kennesaw GA
If you get the 'brake bleeder' (which is a mitey-vac). Make sure you get the one with the gauge on it. That way you can pull a vacuum on devices and see if it will hold or slowly drop. Really the best bet is to get a separate vacuum device for brakes since it will just get fouled by all sorts of nastiness. The $30 Mitey-Vac is the best tool for troubleshooting this problem.
Cruising
Joined: Feb 2006
Posts: 10
Likes: 0
From: Mississippi
Headlights
I bought a hose kit and replaced all of the hoses. Still not working. Can use a vacuum pump to pull the light down. I cranked the car, hit the light switch to turn the lights on and they went up just not down. Im thinking of stripping the vacuum crap and making an electro/mechanical way of opening and closing.
Racer
Joined: Jan 2007
Posts: 325
Likes: 0
From: Ocala FL
You can go electro-mechanical. There are existing kits that make it easier than fabfrom scratch. It will still cost a small fortune.
The vacuum system isn't that bad, it's just old and worn out. The trick is deciding which part to fix, so the troubleshooting guide and a vacuum pump are your best friends.
2 most likely cause of headlight problems are the relays and the check valve. The check valve either dries out or gets some crud sucked into it and now your vacuum reservior isn't charged.
the relays simply wear out. the dogbone slider valve doesn't seal, so your 15 inch manifold vacuum is down to 5 or so at the headlight relays and actuators.
The vacuum system isn't that bad, it's just old and worn out. The trick is deciding which part to fix, so the troubleshooting guide and a vacuum pump are your best friends.
2 most likely cause of headlight problems are the relays and the check valve. The check valve either dries out or gets some crud sucked into it and now your vacuum reservior isn't charged.
the relays simply wear out. the dogbone slider valve doesn't seal, so your 15 inch manifold vacuum is down to 5 or so at the headlight relays and actuators.
Melting Slicks
Joined: Mar 2002
Posts: 2,140
Likes: 7
From: Ohio
I think new hoses is a waste of money unless you want them to look new. If you belive the vendors they love to sell hoses but I doubt they fix the problem 1% of the time. All the parts of the system I have found to be the soruce of the leak and never have I needed a hose kit. I have replaced a hose or two fixing about 20 sharks headlight systems.
I guess you proved hoses are a waste of money!!!!!!!!!!!!!!!
Melting Slicks
Joined: Mar 2002
Posts: 2,140
Likes: 7
From: Ohio
I bought a hose kit and replaced all of the hoses. Still not working. Can use a vacuum pump to pull the light down. I cranked the car, hit the light switch to turn the lights on and they went up just not down. Im thinking of stripping the vacuum crap and making an electro/mechanical way of opening and closing.
I thought hoses was a fix all.
