Another 71 wiper door question, simple??

[Pete B.]

Hi all, I am completing my body off.
I need some help or a resource to get the last piece of my puzzle finished.

1) Wiper door opens and closes beautifully using the pull down override under the the dash
2) When the door is open manually, the wiper high low and washer work via the dash switch

I THINK...that this proves that all the items work.

Can it be the solinoid valve under the dash? How can I test it, or am I going in the wrong direction?

Like I said, it appears that all the components are working, just not in sequence by themselves.
Any help is as always, is appriciated.

Pete

[Jim T.]

Re: Another 71 wiper door question, simple??

Pete I don't have an answer for you, only know the solenoid on my 68 and 70 still function and they are the original solenoids installed when my C3's were built. All the solenoid needs is battery power and vacuum from the engine.

Did you replace the vacuum switch/relay under the wiper grille/cover that functions when the wipers are at rest and actually when the wipers are not at rest?

I have a new one to put on my 70 and it needs replacement. The rubber booted end closest to the windshield has deteriorated and no longer protects what it covers.

If this vacuum switch/relay is not operational, it will not let the wiper door function.

[Kenneth T.]

Re: Another 71 wiper door question, simple??

Pete,

It seems the electrical vacuum switch under the dash is at fault. When you pull the manual stem switch, you are overriding the electrical one and everything is working from that point forward.

That's what I would look at. Good luck.

Ken

[Paul D.]

Re: Another 71 wiper door question, simple??

Pete,
I think you are dead on with your diagnosis. Your first move should be to secure a vacuum diagram and make sure that solenoid is properly tied in. I think it is looped in somehow with the overide button below the dash. You may just have a loose or misrouted hose. I would guess (uh oh!) that you could bench check the solenoid operation with a battery. I would have to do some research as to whether it is open or closed when energized. My dash (71 also) is all out on a table at the moment. I will look at it later if you need anymore info. Chip.
P.S. Just thought about this... make sure a signal is getting to the solenoid. Guess a wiring diagram will be needed also if you dont get a reading at the plug. Those two switches out on the firewall shouldn't be the problem. The electrical one only allows power to the motor after the door is opened and is obviously working. The vacuum switch will not allow the door to close until the wipers are parked and the plunger depressed. I think (uh oh again) that you would not be able to open and close with the overide if that switch wasn't working.Chip.

[Paul O.]

Re: Another 71 wiper door question, simple??

Pete

The way the system works control side small hose.

1. Bleed or lose vacuum
2. Spring in relay over comes the lack of vacuum reroutes mechanical vacuum large hoses.
3. Door or head light buckets open
4. To close vacuum is reapplied to the relay changes to close routing.
5. For wiper door the relay under the door is to make sure wipers are in park before door closes the hose that is cut and open to the engine compartment is the bleed for the control of this function

The first thing I would check is that the wires to your wiper switch is connected correctly. I have found several time working on friends cars that connector is backwards or connected to 2 not all 3 connectors.

The solenoid behind the dash is the vacuum bleed make sure you have power to it and its is connected properly. When you move the switch for the wipers you power the solenoid which then bleeds the vacuum for the wiper door control.

The key to repairing almost anything is to first understand how it operates with that understanding you then have a greater chance of repairing it due to understanding what problem is telling you.

Paul 18046

[Pete B.]

Re: Another 71 wiper door question, simple??

Thanks for the replies,

I'm pretty confident the switch and valve are connected properly.
I have a wiring diagram. I will look to see if I'm getting power to the solinoid.
When it was disassembled all I did was check continuity of the coil on the solinoid valve at that point I just put it back on.

I will report back if I can get to it before going to Kissimmee next week.

Pete

[Jack H.]

Re: Another 71 wiper door question, simple??

There's a complete theory of operation write up on the system in your copy of the 1971 Chevrolet Chassis Service Manual. Read it and you'll understand the pecking order of who does what for the wiper door to open as well as to close. You won't need our advice thereafter...

BUT, one thing that can 'bite' you is the wiper switch itself. It's mounted in the center console and connects to the electro-vacuum relay mounted to the back of the tach. The switch forms a contact closure to ground to activate the relay and that can be a 'rub'.

The center instrument cluster bezel has an intentional weakness designed in (designed to break away in the event of a head-on crash). The bezel is thin at the outside corners just below the A/C vent (or the 'Corvette' label in a non-AC equipped car).

The WSW switch mounts to the portion of the bezel that's above the weak points. If the bezel has been broken (prior Bubba mechanics who didn't read the book on how to R&R the center cluster), it's possible for your WSW switch to be working but NOT making electrical contact to ground due to the broken bezel.

In that case, the vac over-ride switch will get the wiper door up and the WSW switch will apply power to the wiper motor but the WSW switch will NOT ground properly to actuate the electro-vacuum relay on the back of the tach...

[Pete B.]

Re: Another 71 wiper door question: FIXED

Solved!!!!

Problem: Reversed vac lines at the solinoid valve.

I followed the vacuume hose diagram that came with my vac hose kit.

When I removed the solinoid (to test it again) I saw a dab of yellow paint, and I had the white hose connected to that side.
Reversed the hoses, fired it up everything worked perfectly.

Thanks to all for the ideas,

Pete