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Need some input..concerning the headlamps of my '66.

During the assembly phase I also installed the headlight actuators, the new VAC hoses and all the related stuff. I opened the headlight switch, cleaned everything and put it back together. The headlights worked fine from the first test on. The headlight actuators were overhauled at some time from the former owner and I didn't mess with them at that time.
After the car came back together I was more and more annoyed at the way the headlights opened, not quite in uniform. Remember, they opened and closed fine but just not good enough for my taste. So I removed the actuators, opened and cleaned them and gave the inner piston and bore a nice new coat of a special acid free grease. I put all together and the headlights almost snapped open..... but didn't close anymore when the headlight switch is pushed in the OFF position..... Oh yeah... never change a running systemmm I know.. I know.... I removed the VAC container to gain acces to the VAC hoses and T-pieces. The facts are, the lights open, when I switch them OFF the lock blades retract but the pistons do not lower at all. When I open the corresponding T-piece the lights close fine. Only thing I can imagine is the headlight switch. I removed it, disassembled it, found nothing wrong.. assembled it... and still the same.
I am running out of motivation here.... any suggestions?

There is a metal T in the up vacuum line that has a small rubber one way valve. Its purpose is to release the vacuum from the canisters when the switch is turned off.

My car had the metal one replaced with a plastic T with no relief valve. The lights went up but not down.

Mike.

Thx Mike,

I didn't see that T-piece with the integrated check valve. Dou you have a pic of it?
Harald

Just a shot in the dark but, could the newly greased bore for the pistons be allowing the piston to travel farther than its supposed to? Maybe it's getting stuck on a lip or something?

I've never had mine apart so I'm not speaking from experience on these lights but I've seen clutch and brake cylinders behave similarly when the piston travels just a wee bit further than normal.

Here are some pictures of my old T that was missing the valve part. I could not find one, so I replaced it with a four way T and a one way valve. The valve I have is too small so the headlights drop slowly.




Mike.

The vacuum needs a way out of the canisters once the switch is off. That is the reason for the check valve. It was located in the drivers front corner where the lines teed to both lights.
I hope this makes sense?
Mike.

Wow, I never saw that kind of T-piece in my car.... but it went through some hands...
attached is the VAC hose routingof the '66

Here is what I found out:
Switch Off

Switch in ON position

Here's the situation when you switch the headlights OFF, the VAC source is isolated and the power unit connected to the unlatch unit, The VAC in the big canisters overcomes the springs in the unlatch units and they open for some seconds, enough to unlatch the actuating rods. But then where is the bleeding possibiity to unload the VAC in the power units completly.. I don't see it must be an Oldsmobile engineering flaw of the sixties..