74 convertible. Base engine. No a/c. No p/s. No p/b.
Headlamps light up fine using switch but wont lift using switch or bypass.
What i've done so far:
- replaced filter and check valve with new
- tested vacuum line from check valve to input on vac tank - getting good pressure.
- capped one of output ports of vac tank and put gauge on other output- gauge reads zero. Assume tank is bad.

My question - is there a way to run the vac line that is good directly to each of the relay/actuators to see if they are good or bad? If so how?

If the issue is only the tank - how hard to swap? Should i just get a separate/new tank and leave existing there for safety only?

 

*or* if the vac tank is in fact kapoot - should i just go the electric mod route and be done with it ? I like that idea in general but looks pricey.
Id still like to know if i'm only a vac tank away from getting things working (thus my earlier question about how to test each set of relays/actuators with known good vac source)

 

The vacuum tank is reserve only, allowing you to cycle the headlight doors a time or two with the engine not running.

Are you testing with a My-T-Vac or something similar? Have you test the two lines on the rear of the headlight switch?

 

If you car where at my shop I could figure it out in literally a minute or two. The system is SIMPLE.

SO...instead of me typing it all out...if you want me to help you. PM me and I will give you my shop phone number and you can call me and I can talk you through it.....OR...find the procedure somewhere here on the forum and follow it...or possible someone will type it out for you or send you a link from Willcox's site .

I have a stethoscope for listening for vacuum leaks and the rest is common sense tests. If you have a 2 foot section of rubber vacuum tubing ..that can work for you.

No need to get to the backside of the headlight switch...because that control vacuum hose is easy to tell if it is good or not and if the headlight switch needs to be replaced or not.

DUB

 

Here is how to test the relay:


Here is our video on how to test the items in the system:


Here is how to test the actuator:


Here is a vacuum schematic


Willcox

 

Willcox - great stuff there. Thanks. So i have ruled out everything aside of the vac tank and the actuators.
The vac tank my understanding is only there for backup to engine running so i could live without that (correct me if im wrong about the tanks role).

On the actuator i tested with my mighty vac and while i was able to get the door to raise - it took me many minutes of pumping - and i never could it get to to build any real vacuum even after the headlight door raised.

Given this - i need new actuators - agree ?

 

Here is how I quickly check an actuator and I will know in no time that it is good or not. NO TOOLS NEEDED.

HAVE BOTH HOSES OFF THE ACTUATOR RELAY!

SIMPLY..hand raise your headlight door HALF WAY...hold it there....then with the hoses that go to your actuator...you take the hose for the rear section of the actuator closest to the radiator and cap the end of the hose with your thumb. Then apply pressure on the headlgith door DOWNWARDS....IF the actuator is GOOD..you will feel immediate resistance...AND if you release your thumb from the hose while still holding onto the headlight door...you can raise and lower the door and then cap of the hose and feel that is has resistance on it....that tells me that the actuator MAIN SEAL inside it is GOOD.

THEN...do the same thing on the other hose for the hose that comes out the front of the actuator. IF the door will raise and lower when you have the hose capped off with your thumb...NO WORRIES...you can buy the seals for it and replace them. IF it stays put when you apply pressure on the headlgith door when the hose is capped off....then you know the actuator is good.

OBVIOUSLY...if you feel there is a problem...make sure you remove the hose and verify that it is good.

The vacuum storage tank is not there just for your headlights....it is also there for you HVAC vacuum actuators inside the car also. SO...YES...it is important...but you can use the one that GM used on the 1980-1982 which looks like a large coffee can. I am surprised that you vacuum storage in the impact bar is bad...in 30+ years I have only had one that I have had to do work on due to it leaking.

DUB

 

I put a big lift cam motor in my 68 that made only 7" of vacuum at idle and decided to go electric. If you go electric, see Richard454's thread on that. Simple and inexpensive. Got less that 150 into mine and I don't worry about it.

 

Willcox and DUB... First thanks so much for helping me to this point. As a newbie vette owner i knew i would have challenges getting this car to where i want it and so far its been frustrating for sure. Resisting urge to go electrical conversion route just in principle, lol (make mysef work through it).

So DUB - i checked both actuators using your suggestion and they both test good. Relays test good using Willcox video using air hose testing red amd green hises. Im getting good vac to input hose of the vac tank. Gettying good vac to the other hose T connection to relays. I am NOT getting vac with engine running out of vac tank.

questions -
1) is the vac tank required to operate headlights. I want to say No.
2) my lights stay down unless i pull them up, then pull them down. If vac is whats keeping them down as a lot of the write ups say - why dont mine stay popped up ?
3) if i ran vac line from large check valve port all way to yellow hose input on relay - would that be a good test to bypass the vac tank ?

 

Yes you can bypass your vacuum tank to test the system. Your local auto parts store should have a tee that will work. I bought a package of various vacuum fittings when I was troubleshooting my system that cost about $3.

 

So i decided to take the vac hose input to the vac tank that i knew was good and plug it into the yellow hose ports of one of my relays - go fire engine up, pull headlight switch, up she pops. Turn headlight switch off, down she pops. Do same with manual plunger under column - light pops up and down as it should.
Nobody home right now but i let out a small whoop 😄
Thinking now i just need to buy a vac tee with some lengths of hose and route around vac tank !

 

My first victory! I"ll tell ya - it's the little things in life

 

Glad you got it.

DUB

 

Awesome...