1969 wiper door does not work either way.

[Keith G.]

What is the favorite spot to go wrong, have a new wiper door vacuum control ordered, if that does not work I'll try a new solenoid under the dash, the canister seems to be working when I put vacuum to it on one side or the other, then there is the relay valve under the right fender and the control valve under the steering wheel?????? Also how many pounds of vacuum does it take to work the canister?

[Mark E.]

Re: 1969 wiper door does not work either way.

I don't have a specific answer, but the service manual has a nice schematic of the wiper door's vacuum and electrical system and detailed repair procedures which I've found helpful while diagnosing problems. There's also quite a few threads on the wiper door mechanism on this forum and Corvetteforum.com .

[David J.]

Re: 1969 wiper door does not work either way.

The most common issue with wiper doors is the wiper arm safety valve located underneath the passenger wiper arm. If yours is either original or one of the imports, I can almost guarantee that is the problem. Relays are the next thing to go south, particularly if still original. Solenoids rarely go bad, along with the override valves.

There are a few ways to test the safety valve. Try bypassing it by connecting the middle and lower hoses together, and check operation. You can test the vacuum seal in it by putting a Mityvac on the middle port with the plunger extended up, and it should hold vacuum. With the plunger depressed, unplug the lower hose, and replace it with a short BLOCKED hose. Then connect up to the middle hose again, pump it up, and it should hold vacuum. If no Mityvac, try blowing through the middle hose with the lower port blocked. You shouldn't be able to.

To test the relay, hook the Mityvac to the middle port, and block the lower port. Pump it up, and it should hold vacuum. You can do the same test by blowing through the middle port with the lower one blocked. Once again, you shouldn't be able to.

Try these tests and report back.