68-72 Wiper Door

[Gavin N.]

Hi, have been trying to diagnose why the wiper door does not operate on my 1971. When I bought the car I was told the wipers didn't work only to find that they did; then some time after they stop working. Have done some reading in my manual and the board archives to find that its quite a complicated system. My diagnosis to date shows that I can get the door to open when I use the manual override switch; the wipers work when I do this. Problem is I can't get the door to shut using the manual switch. I'm thinking its the vaccuum solenoid behind the dash. Any ideas? Or do I need to do some more tests.

[Chris W.]

Re: 68-72 Wiper Door

Had a similar problem on my 1972, I had to replace a vacuum valve assembly, part number 5638487, located outside on the passenger side under neath the grill, after 30+ years it was leaking vacuum. I believe I sourced the part from Paragon. Check your assembly manual. Otherwise could be vacuum line leak.

[John S.]

Re: 68-72 Wiper Door

The vacuum system isn't too hard to debug and repair. http://vetteworks.tripod.com/techdocuments/Vaccum.html has some instructions. I can email to you a vacuum repari guild if you message me your email address - the file exceeds the attachment limit for this forum.

Trace through the systems to find either places where you lose vacuum or faulty check valve or relay valves.

Replacement hoses and valves can be found at any of the Vette parts vendors. There are also more books on repairing vacuum systems you can purchase.

Look through the filter and I expect you'll be able to see through - replace it.

Remove the check valves and relay valve and blow/suck through them. The check valve should only allow one way flow. The relay valves change the flow through the ports.

Where hoses attach to the valves, t's, etc. the hoses will be stretched out and not provide a good seal. You can replace the host or if only the final 1" is bad you can cut off the last inch and reattach.

You may also find your engine runs more smoothly after sealing up the system.

[Rich G.]

Re: 68-72 Wiper Door

Don't know if you figured it out yet but the door wont close until the wipers are all the way down. There is a vacuum switch that the passenger side wiper pushes closed when it is ALL the way down. If the switch isn't down all the way the door wont close. With the car running push the switch closed with a paint stick. Don't use your hand like I did because if that's the problem the door slams shut on you. Just another thing you can try. Good luck.

[Jack H.]

Re: 68-72 Wiper Door

Also, the valve that the RH wiper arm contacts when it parks is adjustable. The mounting holes are enlongated allowing you to shift it up/down. This dictates when the valve fires to close the wiper door.

On the wiper door not opening, there are TWO cockpit vac switches that control it. One is electro-mechanical and mounts to the back of the tachometer. The other is purely mechanical and it's the over-ride switch beneath the steering column.

If you've read the '71 Chassis Service Manual (gives a GOOD theory of operation dissertation), you know the two switches are in series. Thus, if either one or both vent vacuum, the wiper door opens.

So, you say the over-ride switch works but the automatic switch doesn't. That's pretty simple, the automatic switch is either improperly connected or it's not working...

One reason for dysfunction that's not intuitively obvious is a cracked center cluster bezel. The vac switch on the back of the tach is electrically controlled from the WSW switch that's mounted in the upper portion of the center console.

The center console was intentionally designed to fracture in the event of a head-on collision and MANY have been broken by prior owners/mechanics removing them from the dash improperly. If the bezel is cleanly broken, the wiper switch may not be properly grounding the vac switch on the tachometer...