Would reducing the fitting on the manifold from 1/4" to 3/16" restrict the vacuum needed for the headlight actuators to work?  They both go up about 1/4" then stop. All hoses are new from Docrebuild.  I used the different size fitting because that's what I had on hand.  The bubba who installed this motor and vacuum lines had brake booster to manifold and headlights to carb...oops.  I thought it might be the headlight switch or bypass vavle as those are the oldest components in this system.   I'll probably get some vacuum line and bypass those two components to rule them out or in as the problem.

The size of the line should not affect them. Clean and lube the barrings might help. See if one works better if you plug the line to the other. Check for vacuum leaks. Did you check the actuator valves? Also you will want to check the accumulator tank. Early years it was built into the bumper beam. Not sure when they changed it to a small can. The smaller fitting could cause it to take a little longer to go up but should not cause them not to move. Does it work any better after the car has been idling for a while? This would allow the accumulator tank to charge. 

|UPDATED|7/14/2013 2:22:04 PM (AZT)|/UPDATED|

Do you have a hot cam? 

Size, I mean, not whether or not it's stolen.  That's your bidness. 

Longer idle doesn't make a difference.  I'll get my daughter to help me start checking for leaks.  I still need to try to bypass the light switch and bypass valve.  Wouldn't it be easy if it was the bypass valve?

Sure sounds like you ain't got much vacuum in the tank.  Did they used to work, and just stopped?  If both stopped at the same time, you can bet it's not the actuators and relay valves as they're independent on all but the early C3s. 

Your original idea of jumping the headlight and bypass switches is a good one.  You can rule those out.  There should also be a small filter and check valve in line with the hose that goes from the manifold to the vacuum tank.  You can blow through them to make sure they're not bad. 


BTW, does your tank look like this?  You may want to check and make sure it isn't rusted through or has a split seam.  Plug two of the holes, and put a couple of pounds of air in it (not much!) and submerge it in water, and look for bubbles.

That's a good Idea.  What size coffee can should I use if mine is bad?

Juan Valdez would be proud!

Well, I pulled mine out and tested it. No detectable leaks and I probably put a little too much pressure in it. I by-passed the headlight switch and by-pass switch and there was no change in action of headlights. There is still only a 1/2" movement up and then back down.  It seems strange that they would both act the same.  Any ideas, maybe the check valve or filter?

OK, I reattached the headlight switch and bypass.  I have bypassed the resevoir.  Same problem. If I unplug the line that goes through the firewall and to the switch then plug that side of the check valve with my finger the lights come up 1/2".  when I reattach the hose, they go back down.  When I disconnect the vacuum line between the check valve and the filter, there by having no vacuum at all, they stay closed.

You got me stumped.  You did say that they were both working fine, then both quit at the same time, right?

The only things in common for both headlights on your car are the main vacuum line to the reservoir and the vacuum line from the switch to the relays.  It sounds like the relays are working, as the lights begin to travel, but there is just not enough vacuum for them to move very far.  I'd test the main line going to the tank and blow through the filter to make sure it's not clogged.  Pull the bigger line off, blow it out well, and pressure test it and see what you find.  If you have a cheap vacuum gauge, maybe tee it into the main line going to the vacuum tank so you can see if you're getting a deep vacuum at the tank.

Or you could just begin drinking heavily.

:)