CanadaGrant

I have been chasing a wiper door problem on my 69 for awhile and finally figured it out today. The wiper door/headlight relay valves are spring loaded on the built in diaphragm to the open position with no vacuum. On start, vacuum is supplied to the small port at the top of the valve which overpowers the spring, closes the valve and directs vacuum to the "closed" side of the wiper door actuator. To overpower the built in spring holding the diaphragm in the open position on the ORIGINAL valves only takes slightly more than 1" of vacuum so the wiper door stays closed. On the aftermarket relays it takes around 3" of vacuum to overpower that spring. When the valve is overpowered by the spring on vacuum bleed off to the open position there is still almost 3" of vacuum available which is enough to open the wiper door. Then, on start up vacuum will partially raise then quickly lower the wiper door because it takes 3' of vacuum to overpower the spring an place the valve in the closed position.By that time the door is already starting to open. I imagine one of these cheap aftermarket valves would do the same on the headlights. At first I thought the problem was the wiper door safety switch so I replaced it with one of the good ones from Willcox but the problem continued and I have finally found the new aftermarket relay is at fault as the built in spring is too stiff. I still have the original which I used to compare vacuum readings and it is now working perfectly in the car again. Are reliable US made vacuum relays still available anywhere or do they all come from overseas now?

Big2Bird

I bought 4 Delco units from 2 dealers, and sent them all back. Defective.
I then bought 2 repops from a certain Doctor. They work fine.
He also told me 3 different manufacturers make them.
Which ones do I have? Dunno.

CanadaGrant

Yes, this cheap re-pop passed all the normal vacuum checks for leaks and operation but the wrong spring inside makes it useless for what it was intended. Just goes to show you new and shiny isn't better than old and ugly if it wasn't designed to work...

BLUE1972

ajrothm

My car has the same issue with the wiper door opening on start up and I've chased my tail for years with it. I do have new repro valves on it as well... Maybe you are on to something...

I need to investigate it further.

I know I replaced my wiper door switch which was completely rotted away but the wiper door worked in correlation to the wiper arms closing. I replaced the wiper door switch with one from Wilcox, the one that is supposed to be the "GOOD" one... And now my wiper door closes on the wiper arms.

Its always something with these vacuum systems. I have never been able to get mine to work 100% correct, all the time.

CanadaGrant

At first I thought I was the only one but it seems DUB had the same problem and found the same cause. Read the info in the thread below starting at post 11 and click on his link.
https://www.corvetteforum.com/forums...her-leaks.html