I am trouble shooting a right headlight door issue in my 1968.
Both headlights are very slow up and down.
The left headlight is faster up and down and the right one only rises or lowers after the left one is fully up or down.
The right locks in the up position and locks there even with the engine off.
The right headlight is slower up and down, locks in position with engine running but is easily pushed down or pulled up with engine off.

I replaced the right actuator, the headlight/wiper Actuator Relay and the Vacuum Reservoir Check Valve. No help.
I can hear a hiss when I manually push and pull the right headlight up and down. Using soapy water, I identified the source of the hiss as the (new) actuator relay. Air is passing easily through the bottom of the relay, where the filter is. Is this normal?

Any suggestions on my next step?

 

Use this to test all the parts:
http://www.corvette-101.com/vacuum.htm

 

I will do that. But, can anyone answer one question for me? Should air hiss out of the bottom of the headlight actuator relay when the headlamp door is manually pushed down? I ask because this is a new actuator and I hesitate to return it if it is not faulty.

 

Short answer is yes. The reason is simple. If you think about it, the front and rear chambers of the actuator are connected to the relay by way of the hoses. When the headlight door is raised or lowered, the internal diaphram pushes the atmosphere inside it in and out. The atmosphere must have a pathway to escape. If the relay internal piston is in the lower position, the top relay port is vented to atmosphere through a chamber alongside the main vacuum chamber. If the relay internal piston is in the upper position, the bottom relay port is vented to atmosphere through the main vacuum chamber. Both scenarios are vented out the bottom of the relay.

You can actually check the seals of the actuator and relay by moving the headlight door. You would have to block the middle port on the relay or pinch closed the hose leading to it.

Easiest way to check the relay seals is to remove the middle and lower hoses and attach a short test hose to the middle port. Block the lower port and do one of the following.
1 - Connect a Mityvac or similar and pull a vacuum on the middle port. It should hold vacuum with the lower port blocked.
2 - Simply blow through the test hose on the middle port with the lower port blocked. You should not be able to do it.

Remember, the function of the relay is to switch actuating vacuum between the lower and top vacuum ports without allowing any vacuum to escape, or for the engineers out there, without allowing any foreign atmosphere sources to enter.

 

Thank you, Dave, for your in depth answer. I will check the relay as you describe. Truly appreciated! :-)