MBrianB

OK, I'm just now testing the vacuum system on this resurrection C3.

Hooked up my vacuum pump and as it started to gain vacuum the headlights opened up. Operated the headlight switch and they were already opened and when I turned the switch off they closed. Switch functions correctly when vacuum is applied after the first opening. They just open when I first start the vac after sitting.

I'm learning so much with what has already been done to this corvette before I bought it.

I did connect the headlight switch as instructed with the caveat that if connected wrong there would be a vacuum leak. Well there was a vacuum leak and when I reversed the hoses on the headlight switch the leak went away and the switch operated correctly. The manual pull down works as intended also. So with the wiper pull down.

Anyone have a clue?

bobs77vet

do you have the vacuum hose routing guide?

AllgoodRoger

My brand new 1978 did this when I picked it up at the dealer. Had it back in several times and they and the zone manager guy could never figure it out. They changed all kinds of stuff and then finally found a KINKED vacum hose, folded in half, under the dash, right under the steering column. That was the problem.

Rescue Rogers

maybe a leaking check valve or the headlight switch has a slow leak that is overcome by the constant vacuum of the running engine. Tracing mine i just started at the block and kept disconnecting lines at the connection and going like that until I found mine. I had a 2 season old switch that went bad. I also cut off a 1/4" of hose at each connection if it was easy to get apart

MBrianB

That maybe where I start as I just installed the dash, drivers gauges, and steering column. Not looking forward to taking it out again.

MBrianB

I have checked and rechecked and rechecked every friggin vac line in this entire car and the headlights still open and close on startup...

general ike

DUB

I assume you have NEW actuator relays in it???

Look at this.
https://www.corvetteforum.com/forums...t-problem.html

I figured out the problem...but you need to think about it. And take very careful note what I am showing in the threads..because the answer lies in THAT...if you stop and think about it like I did.

My repair DOES NOT have vacuum leak in the system. It is tight as a drum.

DUB

MBrianB

Every single part and hose is new in my system.

Going to check your link now.
Thanks again DUB.

WOW. Followed the link. Now I'm bummed out. And yes, my wiper actuator opens and closes on startup also.

So what do I do now? Who should I get the relays from?

DUB

Assuming that you have performed a vacuum storage test to make sure your system holds vacuum. This also includes your HVAC system if your car is A/C equipped.

Check this out.
https://www.corvetteforum.com/forums...nk-repair.html

Also this one if you have A/C. POST #13 may interest you.

https://www.corvetteforum.com/forums...d-problem.html

I cannot tell you IF you need new relays. I used the ones I got and fixed the problem. You need to think about what is going on to fix this.


What is happening to these relays when you crank the car??? THEN...what did my previous thread show you???

DUB

MBrianB

IF I had the old relays I suppose I could r&r them in the new relays like you did but I can't.

I'll check the relays today and see what I find. I am using my vacuum pump as the engine is no where near ready to run.

BTW tested the storage tank and it holds 24" with no leaks. The headlight vac system holds 24" also if not actuated. The plenum vac door? Been there and done that also. (not easy nor fun)

DUB

I know you were using a vacuum pump..but I thought that you were NOW using the engine vacuum.

Wait until you get the engine back in and use the vacuum that the engine creates.

TRUST ME...a vacuum pump is NOT always the same as the engine vacuum...or you can be doing something that you do not need to do.

DUB

Antz81

Just tried pumping mine up using my vacuum pump and both headlights opened one before the other when they should have stayed closed. If I try the system using engine vacuum then it functions perfectly.

MBrianB

WHEW!!!!

DUB

I am glad that Antz81 confirmed what I wrote is TRUE! A vacuum pump does NOT provide the same effect the as the engine vacuum.

BUT the problem CAN still exist.

Lets hope not.

DUB

DUB

Antz81

Wasn't doubting what you said was true for a second. Just wanted to see it for myself. Only surprise to me was both lights opened about 1/2" and then from there opened one at a time.

DUB

I did not want to come across that you doubted me...because many people here on the forum do. Which is just fine and dandy.

So when someone like yourself confirms the stuff I write. I am glad that it is confirmed....that's all. Just lets me know I have not gone totally insane yet.

I am GLAD you took the time to see for yourself. The LAST THING I want to do is to steer someone into the abyss. God knows I have been there more times working on these Corvettes than I care to admit or want to remember.

DUB

MBrianB

Yes it can....

Now that I have the engine running, every time I start the engine the headlights open and close. I also hear the wiper door actuator doing things but since there is no door or mechanism installed I don't see anything happening.

I have checked and installed new vacuum check valves. All the hoses, actuators and vacuum valves are new and everything works like it is supposed to when the lights go on and the heater controls are operated.

Stumped.