I am still working on the lights. This vacuum stuff is way more complex than electric. I started by swapping out the headlight switch for a new one from Ecklers, but it did not solve the problem or seem to have any impact. So I started checking the things you listed.... I checked number 1 and with the lights off and the bypass pushed in/up under the dash- I get vacuum to #1. Not a lot, but it is there. So I started playing with the lines at the relay's swapping them to see if it made any difference if I used the Left relay with the right headlight. No real change. Next I tried bypassing the relays hooking each actuator directly to the tank. This closed both lights. I then hooked everything back up and the doors stayed down. Which surprised me because I thought when I disconnected the hoses I would have lost vacuum and the headlights would have opened. Anyway, I pulled the switch and the both doors started to open very slowly. The passenger side made it up after 20-seconds. The drivers side took over a minute to open. Neither would go back down after they were up. So next I tried blocking off one side at a time at the tank. Each time the unblocked side worked like a champ. Very fast, up and down. Which has me thinking it is neither the actuators or relays. I am lost. The tank seems to have plenty of vacuum. I don't have a gauge, but it is pretty strong.

Any help would be greatly, very greatly, appreciated. I feel like I am in a foreign country and don't speak the language.

 

Still working on it. Selfish bump to see if anyone has any thoughts. Tx, Bill

 

http://forums.corvetteforum.com/c3-t...tem-works.html


Keep the shiny side up!
Scott

 

Since everything worked when you plugged one side at a time, it sounds like you might have multiple minor vacuum leaks that can be overcome by the tank vacuum when isolated to one side at a time, but when everything is hooked up there is enough vacuum loss that nothing works. Since your driver side took a minute to come up, I would suspect it has more vacuum loss. Try plugging the hose ends at the actuator on the driver side. If the passenger side doesn't work then you know that you're losing vacuum before that point. Then, one at a time, plug the relay fittings for the red stripe and green stripe hoses. If you get the passenger side to work, then you know that the hose you just took out of the system is leaking. If that doesn't make it work, then plug both fittings at the relay at the same time. If that makes the other side work, then replace both the red and green stripe vacuum hoses. If it still doesn't work then plug the yellow stripe hose at the relay. If that makes the passenger side work then you probably have a problem at the relay, if not, then you may still have a problem with the actuator or minor leaks at both the relay and the actuator. Repeat the process on the other side.

Good Luck.

 

Usually, if mine don't go down, I lightly lift up on them while the car is running and they always go down. Give that a try if nothing else.

 

I'd like to reiterate...

The Corvette assembly guide that I have shows the vacuum hose with the blue stripe going
to the rear port on the head light switch. This is incorrect. The hose with the blue stripe goes to the forward (towards engine) port on the switch... simply switching the two hoses solved my vacuum issues and I'm now ready to move forward with my project.

I've just spent two days trying to diagnose the vacuum problem after removing my dash and using the assembly guide as a reference for reinstalling the hoses.

http://forums.corvetteforum.com/c3-t...tem-works.html

^^ as previously posted, this link is the cats a$$ on headlight vacuum schematics... check it out.

mardyn

 

Then they will never go up again

 

Hi there. Wondered if you were able to assist me with my headlights. I have just imported to the UK. It arrived with both headlights up. Battery totally dead. Once Recharged one went down and the right stayed up. The light switch is an issue in that the black pull switch keeps coming off when pulled out. Anyway of fixing this? All lights light up so no problem here.
Thank you in advance. Simon

 

Hi there. Wondered if you were able to assist me with my headlights. I have just imported to the UK. It arrived with both headlights up. Battery totally dead. Once Recharged one went down and the right stayed up. The light switch is an issue in that the black pull switch keeps coming off when pulled out. Anyway of fixing this? All lights light up so no problem here.
Thank you in advance. Simon

 

The headlight **** rod locks within the headlight switch to keep it from pulling all the way out when you turn the lights on. You may need a replacement light switch if the rod will not lock in place.

 

I have the same problem on my 76 after having a new master cylinder put on (related?). No vacuum at #1 hose. Do not see pull down switch, where exactly is that? Under dash cap?

 

I was wondering if anyone knows about why the headlights wont go down on c5 corvette after starting the car and turning the setting to off. They do sometimes but not all the time as of tonight they wouldn't at all. I assume that its not a fuse because it random and they go up and down when I start and turn off the car. I was wondering what ground I should check or what wires in the fuse box? or the blinker is bad but everything else on the blinker works just fine which leads me to think that it is the grounds. thanks for your help you are a big help!!

 

Go up after starting ... will not go down after engine shut off?