Hello All,

I've got myself a 1969 L36 which runs seemingly well. I've noticed the wiper door didn't want to come up. I greased all the moving parts and replaced the wiper door vacuum actuator (the part that waits for the wipers to dock themselves). I've noticed one of my headlights doesn't go up as fast as I'd expect them to. Well, I purchased a vacuum pump, threw vacuum into the intake manifold port so I could power the entire system, and heard some leaks.The vacuum relay that is located on the passenger side seems to leak out of the bottom of the piston. So I was thinking I needed to replace the relay. Well, since I was replacing that one I figured I'd also replace the headlight vacuum relay. After replacing both of them and hooking up the system to my vacuum pump again neither the wiper door nor the headlights work. I start up the car and it runs perfectly fine until I try to turn on the headlights then it dies. I replace the vacuum relays with the old one's and try everything again. Runs fine, headlights go up slowly, but at least don't kill the engine. So I'm thinking that the two vacuum relays I purchased were bad so I ordered from another website (midwest corvette versus zip-corvette). Same thing happens with these one's as well. The new vacuum relays again kill the engine as soon as I try to turn the headlights on. I'm stumped on how to move forwards.

I tested out the new vacuum relays by the following videos: and
- New vacuum relays are killing the engine when I turn the headlights on and do not pop up in the slightest
- Old vacuum relays are NOT killing the engine when I turn on the headlights and pop up slowly
- New vacuum relays are passing the tests shown above
- Old vacuum relays are NOT passing either test shown above.

What in the world is going on...Am I missing something simple? New relays and old relays are hooked up in the same direction with the same colored hoses going to each port.

 

Look at the Willcox Technical site under Headlamp Vacuum Diagnostic Help. It may be your check valve, have you tested it?

 

You can do this test when the relay is in the car but I suggest pulling it just gives you a better visual of what the spool is doing.
Remove the small piece of foam on the bottom so the end of the spool is exposed.
If doing it in car remove all vacuum hoses from relay.
Take a #2 pencil using the eraser end and press the spool in then remove pencil and see if the spool returns, it should spring return on its own.
Do this several times to make sure the spool is moving freely.
Now, pull a vacuum on the top small port of the relay, this is the vacuum signal port from the headlight switch.
This should hold a vacuum and you should see the spool of the relay move like the 2nd video shows, do this a few times.
If the relays diaphragm is holding vacuum and the spool is moving freely in both directions then you know that portion of the relay is working correctly.
If your wiper door relay is leaking out the bottom it sounds like the relays spool is in-between ports and is exhausting.
The headlight actuator(s) and the wiper door actuator has to release its energy somewhere to change state.
They exhaust out the bottom of the relay.

 

I have not tested any of the check valves. Let me do that today. Thank you!

 

I'll go ahead and do that today. I do know the old vacuum relays were not holding the vacuum described in the first video above but were able to hold the vacuum to get the piston to move up and down. It would just leak out slowly. I'll test again with the new vacuum relays to see if there is an issue. Thank you!

 

Remember, there are 2 different vacuum sources to the Relay, Signal and Main.
You can see that in the 2nd video he used 2 vacuum pumps, one to the signal circuit from headlight switch and one used as the main vacuum circuit operating headlight actuators.
So if the top port (signal) is holding a vacuum and the spool shifts freely I would check that off the list as the problem area.

 

like an electric relay. small power circuit throws the switch which activates the big bower circuit. your old relays. lights raise slowly. that is not a vacuum issue. that is an atmospheric pressure issue. the hole the spool is in. look at the smile shaped hole next to it. when raising headlights, air flows in that hole through the back side of the control vacuum pot to the top big hose in the relay out to the actuator. you put vacuum on one side of the actuator and light can not move until you blow the other side with air pressure. there is a bug nest in the smile shaped hole blocking the air flow. and these relays don't have to be perfect. they supply less air to the intake than the PCV valve if leaking badly. and the replacements seem to have too-stiff springs in the control circuit that will cause lights to pop up then close on start up. the storage can can be a big vacuum leak. a large 3 way T fitting plugged into the big lines to eliminate the tank is a way to test that.

 

As a last resort, use a smoke machine/tester. I have used one in the past and it helps out a lot tracking down those really pesky leaks that are hard to find. You can even make your own...

 

Ok,
Not really how I would test the valves because that is not how the vacuum is passing through them in the later videos. Can you send me a picture of how you have your relays hooked up. Let's start from there and see if we can figure out what is going on.
Thanks

 

post pics of how you have them hooked up....i bet you crossed a line somewhere. But any way, the small black hose with the white stripe is the signal line and it goes to the top of the actuator relay. THe black with yellow is the work vacuum hose. the green and red stripes open and close the doors.

Some helpful hints

When you use an electric vacuum pump, use a vacuum gauge so you dont over power any of your seals IF you let that thing suck down into the 30s its wont end well 20inHg is as high as you need.

I use a christmas tree light plug remote, super cheap at Michaels to turn my vac on and off so I can watch the gauge from across the car. Just leave the switch on and use the remote to control the plug. turn it off then use a stethoscope to listen to the vacuum connections for leaks. If you dont have a stethoscope stick a length of vac hose in your ear and use the other end as the stethoscope. It will localize the leaks.

YOu can separate the systems from each other to localize leaks and determine if one system is effecting the other. One tee is under the dash and splits to send one hose to the headlight switch and one to the relay on the back of the tach. If you have a clamp or hemostat you can clamp off the hose you arent testing on the signal side. IF you want to test the work side you have to find the hoses that supply the actuators for each door and clamp those off after the vacuum tank where they split

 

I went ahead and made a video if that's okay. I can still sit down and translate to paper if needed.

https://photos.app.goo.gl/yHmoZWmUdoXmGKpP6

What I'm confused about is if I swap the relays with the brand new ones I bought my engine dies when turning on the headlights. Exact same hose positions. I haven't had time to properly sit down and diagnose a possible check valve issue someone mentioned earlier. I will also take this graphic you've provided and over the weekend and guarantee it is the same. Mine is an early 69 as well.

 

good job omn the video. It looks like you have everything hooked up correctly. If you hook a vacuum pump up to the manifold connection can you get the system to work? THe reason your car dies is you are introducing a huge vacuum leak. So one of those systems is now leaking profusely. If you over vacuumed the system while testing it that could have happened. Test the system with a pump as it sits, with the car off and if it works we need to look elsewhere but I believe it wont. What you can do is clamp the yellow hoses at the tee going into thte vacuum tank on the drivers side and start the car. Then try to open the headlights or the wipers and see if the car dies. the unclamp one of the 2 systems and try it again. Re clamp and unclamp the other. You can track down where the leak is

 

When testing cars here, I have had hoses unplugged and while the running condition changes it is never enough to cut a engine off. You may have more than one issue going on with that, but it is obviously somewhat related. First step is testing to make sure your vacuum tank is good. You can get a cheap emission smoke machine from Amazon. They way you test this is to first smoke the tank and see if you have leaks, make sure you are using as little pressure on the emission machine as possible, you do not want to pressurize the tank. The tanks get cracks and rust on the inside, the pressure can seal the tank but under vacuum they can leak. The smoke machine is to point you quickly to issue. If there is not smoke present then get a vacuum pump and see if the tank will hold vacuum. The next step is I would replace all those lines, they are original on your car as you can see what is left of the strapping tape. The lines being dry rotted and cracked will also leak vacuum, and a bunch of little leaks make a big leak. I would start there, when all these parts are in good shape, if you unplugged one of the vacuum lines the car should not cut off.

 

Looking at the schematic, there is only one 'control' hose, so a binary 'vacuum' or 'no vacuum' determines the 'close' or 'open' states, I think. Default, I assume, is 'no vacuum' and therefore 'open', yes?

 

https://www.harborfreight.com/25-cfm...ump-61245.html

Get one of these... get a LONG hose (its a loud pump)
put the pump outside and run the vacuum hose into the garage and hook it up to you vacuum port instead of using manifold port..

You now have vacuum for the entire system... AND, you can hear every single leak
p

 

Those pumps aren't that loud IF you put oil in them!

Seriously, I have one of those HF units and I don't think it's load at all - I guess hearing loss is another sign of old age

 

You guys are on the right track.

I tell this story a lot.
Old timers I hung around showed how to plug in an air compressor hose's nipple to my pickups PCV hose,
Then ran the hose over to the stink'n stingrays head lite hose of my choice.

Started up the truck.

Man , I could hear every leak there was..................

God bless those guys.
R.I.P. Blithe.







keep looking up and smiling.