Hello Forum,
I have been battling with my 1968 headlight operation for over a month now with no progress. There was a failure to close with headlight switch turned off.
I isolated the system from the wipers so I could trouble shoot.
Wiper seem to work isolated from headlights but with headlights on same source it seems like too much of a strain on vac supply.
I have read and reread all of the headlight trouble shooting on this forum and watched Wilcox's video's on testing and repairing the individual components.
I have replaced both headlight actuators, the relay was recently sent out to another forum member and rebuilt(thanks Dave J).
I have all new hose lines from a kit I purchased and I installed every line.
I even took the dash out to get to each one.
I double checked for correct line placement.
I tested the headlight switch it holds vac closed.
I'm getting 19 lbs of vac at the manifold orifice.
This is my base line vac.
It is still reading 19 through the filter, check valve, and holding tank in the fender. Tank fills quickly as gauge goes up to 19 in no time.
This is where I'm stumped....
When I hook up the small line and larger yellow coded supply lines and check them at the opposite ends(relay side)near nothing on the gauge
I know the logical answer would be a leak or blockage.
I took off the lines and blew air through them and checked to make sure they held vac. Pull downs under dash closed and checked they hold.
It seems like there is a loss of vac. as it's not making it to the relay both at the control line and source line.
I started the car and the lights came up very slowly barely to be more accurate.
When I put the miti-vac on the top little control line port at the relay and pump it up it takes 4-5 lbs to lower both lights.
They both went down as expected normal speed.
Now why wont the car do this on it own as designed?
I'm not getting any vac to control line port at relay, and source line is obviously dropping off somewhere as it's so low it barely moves the lights.
I double checked my route of the lines no binds or bends to cause a restriction.
With the new parts these things should be snapping up and down smartly. One would thing?
Oh well open to all ideas.
Thanks,
Marshal

 

If your hoses are connected correctly the usual problem is a bad relay valve because they don't last very long. The relay valve cal easily be checked by sucking on the center large nipple (with a hose attached) while plugging the bottom nipple (opposite the diaphragm end). It should hold vacuum and yours probably doesn't because the seals on the little spool inside are shot.

 

Marshal, I suspect two scenarios for you to check. First, connect your vacuum gauge to the small (control) port on the check valve, start the car, and check the vacuum. You should have the same (19lbs) there. If not, replace the check valve. There should be free passage of vacuum between the two ports on the same side. I have seen these valves get clogged inside and not allow free flow inside them. You can also temporarily replace the check valve with a 3 way connector, and everything should work if it is indeed the check valve.

Second, you checked the headlight switch to hold vacuum when closed, but how about when the switch valve passes vacuum through it? You can isolate the switch and creatively block the control hoses to allow the switch to be checked without taking the dash back apart.

I suspect the check valve first. Get back hold of me if you have any more issues.

 

I just did this on mine also, look at everything separate. Lights, wipers and then controls.
Before i start, the way you wrote a couple things needs clarified, you say light switch and overrides are all closed and hold vac? These should be open to allow vacuum path,

First. If the large opereating line from tank to light relay and then actuators is not getting vac. Then fix that...no use doing anything else yet.
You get vac at the can? Try a short hose...maybe the port is plugged.
Then when you have vac at the relay, put your little pump on it and operate it, make sure the lights go up and down.
Do the same with the wiper door.

Then we can go through the control side...
I found some good pics and diagrams if you need them

 

Gentlemen,
thank you for your responses to my problem.
I usually can fix most man made things automotive related.
This one has given me an anxiety attack.

Dave, I have 19 at the check valve either port with one side blocked.
I was incorrect when we spoke on the phone.
With the large yellow line hooked up to the check valve,
I have 0 at the small port. If I had 19 I could just proceed
to the headlamp switch, tach solenoid and pull down switches.
I replaced all the rubber lines so that was the reason I removed the dash.
I initially did just under the hood, so yesterday I finally finished the job.
As soon as I hook up the yellow service line it seems there is no vac for the little port on the check valve. I tried a 3 way tee and still no vac to small lines.
It has got to be something stupid I'm missing here.

Too broke to retire, relays are good. I checked them again to be sure.

Skip99202, Oddly enough with the check valve in place, small port capped off, the holding tank will fill to 19 inch vac and the tank will remain at 19.
When I remove the vac gauge from the lower tank nipple and reattach the service line running to the relay, I then checked at relay and vac in almost no existent.
I know at this point you guys must thing I'm playing stump the chump with you all, but I am reporting my findings this is really weird???
I had to walk away from it today as I'm outta ideas.
Thanks,
Marshal

 

Pm sent

Has to be a leak in the line to the front relay..or the hard line going to passenger side wiper relay..