RS vacuum headlight help

[sdkar]

I have a couple of questions.  First, the main line (the larger black tube with no markings) that comes from the headlight switch to the "Y" at the tank...when should this have suction?  When the headlights are ON or OFF?  Mine have suction when the headlights are OFF.  When should the tank relay have suction and at what nozzle (The R or the G nozzle)?

What is a good way to diagnose the relay switch itself.  If I put suction at the smaller hose with the red stripe at the top where the bypass switch is, it holds suction perfectly. 

If I bypass the the tank and switch and put suction on the green and red hoses, the doors open and close perfectly. 

When I turn on my headlights, the suction goes away at the main line.  I know my problem is somewhere at the tank/switch area.  Any ideas to find out what exactly is the problem?  Is the tank supposed to help with the suction or does it provide the vacuum necessary to open the doors and the vacuum line's job is only to make sure the tank has vacuum all the time?  (Does that make sense?)

My tank holds vacuum and has no leaks.  My actuators are working fine and open and close when vacuum is put to either side.  So, I am thinking it has to be the relay.  However, before I go changing mine out, I want to make sure.  My relay is original.

Anyway, any help in diagnosing my problem is greatly appreciated. 

Thanks guys,

Steve

[rich69rs]

Steve,

Take a read through the attached if and see if it helps.

With the engine running, the headlights off and the override switch (manual switch on top of the 'Vacuum Relay')  in the normal position there will be vacuum present on the:
- black hoses
- the yellow-striped hoses
- the ‘Vacuum Tank’
- the middle port of the ‘Vacuum Relay’

You will also find vacuum present through the headlight switch and on the orange-striped hose from the headlight switch to the ‘Vacuum Relay’ and the green-striped hoses to the actuators.

As far as the relay switch, I am assuming that you are referring to the manual switch on top of the Vacuum Relay.  If you slide it from one position to the other, do the doors open, then close when you slide it back?  If nothing happens, most probable cause is either the internal diaphragm in the top of the Relay Valve is leaking or the pilot valve in the realy body is stuck.

If you carefully feel under the relay valve with your finger, you will feel the stem of the pilot valve that is inside the Vacuum Relay.  Carefully try to push it up.  You have to be careful because it is connected to the diaphragm in the top of the Vacuum Relay.  You should be able to gently move the pilot valve.  If it moves, then you know it isn't stuck. 

Richard

[Mark]

Repro relay valves are labeled wrong.  the red striped hose, goes on the port with the G on it, and the grennd striped hose goes on the port labeled R.  Vacuum is applied to the relay valve to keep the headlight doors closed, so there should be vacuum there whenever the car is running, and the headlight switch is off, or in the parking lamp position.  the vacuum tank is there as a surge volume to allow the headlights to operate smotthly and to provide adequate vaccum to close the doors after the engine is shutoff, and the vacuum source is gone.   Original relay switches tend to get gummed up over time and stick in the closed position.  Vacuum is supplied into the relay valve thru the center port, and goes out to the back of the actuators thru the green lines.  In the closed position the red lines are connected to the oposite end of the actuator and vent thru the bottom center of the the relay valve.  As the actuators age and allow more air to bypass the seal on the piston inside the actuator the system starts sucking engine compartment air into the bottom of the relay valve.  This air contains oil mist, raod duct and anything else floating around the engine compartment.  This gunk sticks to the side of the piston inside the relay valve and eventually the valve sticks in the closed position (most of the time).  Pull the valve off the vaccum canister, flip it over and use some kind of degreaser, like an electrical contact cleaner and spray it up inside the center of the valve from the bottom.  then exercise the valve open and closed with the manual override lever on the top, or push up on the pisting from below.  It will eventually free up and start working after a couple of minutes.  Put it back in and see if its any better.

[jacmac]

Mark is correct!

[69pace]

Well not really. After considerable discussion over a TC a year or so ago we all discovered that actually looking at the 68 and 69 AIM straightened out many misconceptions about the vacuum headlight systems.

The 1969 "Vacuum Control Relay Assemblies" were plumbed like a traffic light green on the bottom and red at the top. See attached photo of page 463 from the 69 AIM. Actuators were red in the front green in the rear

However Original 68 Vacuum Control Relay Assemblies were just the opposite with green at the top, and red hose at the bottom - see page 431 of the 68 AIM    Actuators were red in the front green in the rear.

The repro valves on the market manufactured by Classic HQ now are marketed as 68-69 generic and use the 69 design red on top so if using one on a 68 you have to watch the code and connect the hoses like a 69 red on top green on bottom otherwise the doors work in reverse. Also check your activators for red front green rear otherwise doors will also work in reverse.

[Mark]

There is a set of repro relay valves out there labeled green at the top, red at the bottom I had a set after my original failed back in the mid 80's.  That one has since been replaced with another repro that is labelel red on the top, green on the bottom after the first repro sprung a leak in the diaphragm. 

Obviously the 68 headlight switch operates in reverse from the 69 if the hoses on the valve are backwards but the hoses on the canisters are the same as a 69.  On a 69 vacuum is present on the top of the valve diapragm whenever the headlights are off and the car is running, so the shuttle in the valve is pulled up, and the yellow center port is connected to the green bottom port, and the red top port is connected to the vent in the center of the valve and this keeps the doors closed.  When vacuum is removed the spring on the top of the shuttle pushes it down and the yellow center port is connected to the red port, and the green port is connected to the vent in the center of the valve and the doors close.  68's must have provided vacuum to the valve diaphragm from the light switch to open the doors, (valve pulled up yellow connected to green) and vented that line to close the doors (yellow connected to red).  Now the question, how does the door override work on a 68, since all it is is a plug to block off vacuum to the actuator if its actually plumbed the way the AIM shows?

[sdkar]

Is there a way to check if the vacuum relay is bad or not?  Is there a way to open this up and take a look?  I believe this is the part that is bad and why my doors do not function properly.  Everything else looks in order.  So, before I spend money for a new one, what do I check to make sure first?

Thanks,

Steve

[Mark]

With the car running and headlights off , put the override switch on the relay valve on (push it in).  If your doors don't move stick you finger (or something short and skinny -  like a 2" long 1/4" dowel) up into the bottom center of the relay valve and feel where the shuttle is inside the valve.  The lower edge of the shuttle should be right at the bottom of the body of the valve.  If its up about 3/8" into the valve body it is probably stuck in the up position (yellow hose connected to red hose = doors closed)   If its at the bottom, or pretty close to it release the override and you should feel the shuttle should move up about 3/8", again if it doesn't move its stuck in the up (doors closed) position.  Swap the red and green hoses on the valve and make sure the doors open.  Put the hoses back to their original positions (red on top, green on bottom) doors should close.  If it acts this you have now proven that the inner shuttle is stuck and/or disconnected from the vacuum diaphragm in the top of the relay valve.  Take the valve out, and soak the bottom half of it (the vertical palstic part) in some kind of mild degreaser/parts cleaner.  Maybe start out with a hot dish soap solution to try and clean out the oil and grit holding the valve in one position.  If that doesn't free it up, there is a way to disassemble the valve, but i haven't done it in about 20 years so I'm not going to try and guess at it now.  End result is you have to get the inner shuttle loose and moving to get the doors working.