1969 Wiper Door Vac Safety Switch - Interlock Valve

[Lawrence M.]

This is the vacuum valve that is depressed by the right side wiper arm when in the park position. According to Dr Rebuilds vacuum diagnosis instructions this valve should maintain vacuum on the unmarked (top) port when the plunger is depressed. I have bought 2 NOS valves and niether will hold vacuum on the unmarked port when the plunger is depressed. Both valves will hold vacuum on the white port when the plunger is released. The valve that was in the car would not hold vacuum at any port.
Is this valve supposed to hold vacuum on the top port when the plunger is depressed? I have not tried a repop yet as I thought NOS AC Delco would be the better part. Do I just keep buying valves until I find one that works?

Larry

[G A.]

Re: 1969 Wiper Door Vac Safety Switch - Interlock Valve

Can't remember the answer to the vacuum question, but.......
I got one of Doc's NOS valves. Took about an hour and a half to get the thing "dependable", meaning it took silicone and a lot of adjusting the rubber bellows to finally get a good seal that would pass the leak-check. Also, I "re-adjusted" the bracket the valve bolts to, to get the 1/2 travel AIM calls for on the plunger. I had a repop and it was crap.

Dan

[Lawrence M.]

Re: 1969 Wiper Door Vac Safety Switch - Interlock Valve

I'll work on the valves with silicone and see if i can make them work. I thought the rubber bellows was just to keep dirt out of the valve.
Thanks for the reply, at least I know I'm not the only one that has experienced a poorly operating NOS valve.

LM

[Jack H.]

Re: 1969 Wiper Door Vac Safety Switch - Interlock Valve

Consult your copy of the Chassis Service Manual, Section 12, Electrical-Body Chassis, Corvette Wiper Panel. You should find a nice theory of operation exploded diagram of the various vacuum devices.

The Vacuum Control solenoid (back of Tach), Over-Ride Switch (below the steering column) and Interlock Valve (cowel) are ALL in series with each other as far as the control side of the vac system goes. Vent vac at one or more of these and the wiper door opens. To close the wiper door ALL THREE have to pass vac...

Simple...