Headlight won't go down
09-26-2003, 11:01 PM
#1
Le Mans Master
Thread Starter
Headlight won't go down
My right side headlight will not go down. I'm going to check all hoses tomorow, but is there one specfic problem that causes this?
09-27-2003, 12:05 AM
#2
Advanced
Member Since: Feb 2003
Location: Cleburne Texas
Posts: 93
Likes: 0
Received 0 Likes
on
0 Posts
Re: Headlight won't go down (Paul 75 L82)
Hey Paul,
I have the same problem. I am almost positive mine is because of the relay. I hooked up the red hose straight to the vacuum tank and it pulled it down. Could also be the actuator has gone out. Good idea to start out with the hoses though. I found this website VERY helpful www.corvette-101.com Until I replace it, I just bubba rig it and pull it down myself during the day :thumbs:
-Karl
I have the same problem. I am almost positive mine is because of the relay. I hooked up the red hose straight to the vacuum tank and it pulled it down. Could also be the actuator has gone out. Good idea to start out with the hoses though. I found this website VERY helpful www.corvette-101.com Until I replace it, I just bubba rig it and pull it down myself during the day :thumbs:
-Karl
09-27-2003, 12:17 AM
#3
Le Mans Master
Re: Headlight won't go down (Paul 75 L82)
If it is a recent problem, and since only one is not working, it is most likely a vacuum leak.
The headlight assemblies are raised and lowered by vacuum motors that you can see clearly when you raise the hood and look down between the hood and the rear of the headlight assemblies. Each motor has two large vacuum hoses coming off it that are connected to an actuator relay valve. The actuator relay valve(s) are attached to the underside of the nose between the two headlight assemblies. If you stand in front of the car with the hood up, look into the opening back towards your feet. Look at the underside of the nose and you will see the relay(s). (I can't recall if the 75 has one or two, my 73 has two, one for each headlight assembly.)
The relay(s) have a small vacuum hose that goes through the radiator support and ultimately connects to the headlight switch. When you pull your headlight switch on, it ports vacuum to the relays which move a sliding valve that ports vacuum to the headlight motors through the larger vacuum hoses. There are three large hoses on the actuator valve. The center one goes to the vacuum reservoir and the top and bottom go to the headlight motor. These lines are a tight fit and often stretched tight as well. It isn’t unusual to have one disconnected or loose enough that the vacuum leaks rather than move the motor. I would check these carefully.
Since one is working you obviously have vacuum to one of the relays and operating the one motor. If there is only one relay, it will have both headlight motors tee’d into the single relay. If you have two relays it makes troubleshooting much easier. If all of the vacuum lines appear to be tight and in good condition, you can swap the lines from the good side (relay) to the headlight that is not operating to see if it will work. If it now works, then you have a bad relay and they’re about $60 from many of the Corvette vendors. If it still doesn't work then go to the next step.
Reconnect all of the hoses as before and then pull the headlights on. Manually raise the headlight that is not coming up. If you can then lower both headlights by pushing in the headlight switch, the problem is a leaking motor. The motors use vacuum to raise and also to lower the headlight assemblies. The front of the motor has an actuator rod protruding from it that actually raises and lowers the headlight assembly. There is an actuator rod seal and a dust boot around the actuator rod that seals the motor so vacuum can pull the diaphragm forward, extending the rod and raising the headlight assembly. The dust boots deteriorate pretty quickly, but the seal is quite sturdy and holds up long after the dust boot is shot. The seal and dust boot are both available from most of the Corvette vendors as well and at about $20, considerably cheaper than buying a new headlight motor.
You can also tell when you have a bad seal, because the headlights come up slowly or not in unison. When the seal is leaking enough the motor will no longer raise the headlight assembly. However if you pull them up manually, they will almost always go down correctly. This is a sure sign of a leaking headlight motor seal.
Sorry for this being so long, but the headlights on the C3’s are really one of the simplest systems on the car if you understand how they work. Yet I still see too many C3’s running around with their headlights up all of the time because people think it’s too complex or too expensive to fix.
Hope this helps…
GUSTO :)
The headlight assemblies are raised and lowered by vacuum motors that you can see clearly when you raise the hood and look down between the hood and the rear of the headlight assemblies. Each motor has two large vacuum hoses coming off it that are connected to an actuator relay valve. The actuator relay valve(s) are attached to the underside of the nose between the two headlight assemblies. If you stand in front of the car with the hood up, look into the opening back towards your feet. Look at the underside of the nose and you will see the relay(s). (I can't recall if the 75 has one or two, my 73 has two, one for each headlight assembly.)
The relay(s) have a small vacuum hose that goes through the radiator support and ultimately connects to the headlight switch. When you pull your headlight switch on, it ports vacuum to the relays which move a sliding valve that ports vacuum to the headlight motors through the larger vacuum hoses. There are three large hoses on the actuator valve. The center one goes to the vacuum reservoir and the top and bottom go to the headlight motor. These lines are a tight fit and often stretched tight as well. It isn’t unusual to have one disconnected or loose enough that the vacuum leaks rather than move the motor. I would check these carefully.
Since one is working you obviously have vacuum to one of the relays and operating the one motor. If there is only one relay, it will have both headlight motors tee’d into the single relay. If you have two relays it makes troubleshooting much easier. If all of the vacuum lines appear to be tight and in good condition, you can swap the lines from the good side (relay) to the headlight that is not operating to see if it will work. If it now works, then you have a bad relay and they’re about $60 from many of the Corvette vendors. If it still doesn't work then go to the next step.
Reconnect all of the hoses as before and then pull the headlights on. Manually raise the headlight that is not coming up. If you can then lower both headlights by pushing in the headlight switch, the problem is a leaking motor. The motors use vacuum to raise and also to lower the headlight assemblies. The front of the motor has an actuator rod protruding from it that actually raises and lowers the headlight assembly. There is an actuator rod seal and a dust boot around the actuator rod that seals the motor so vacuum can pull the diaphragm forward, extending the rod and raising the headlight assembly. The dust boots deteriorate pretty quickly, but the seal is quite sturdy and holds up long after the dust boot is shot. The seal and dust boot are both available from most of the Corvette vendors as well and at about $20, considerably cheaper than buying a new headlight motor.
You can also tell when you have a bad seal, because the headlights come up slowly or not in unison. When the seal is leaking enough the motor will no longer raise the headlight assembly. However if you pull them up manually, they will almost always go down correctly. This is a sure sign of a leaking headlight motor seal.
Sorry for this being so long, but the headlights on the C3’s are really one of the simplest systems on the car if you understand how they work. Yet I still see too many C3’s running around with their headlights up all of the time because people think it’s too complex or too expensive to fix.
Hope this helps…
GUSTO :)
