70 windshield wiper adjustment?

[Mike F.]

Just bought a 70 coupe two weeks ago and the wipers probably haven't run in about 15 years. (Last owner had it 26 years)

I had the wiper motor rebuilt at Wiper Works. Works great and looks great.

Sit it car, turn on wipers, door opens up, wipers work, turn off wipers, they park.
The only problem is the passenger side wiper parks about .5" to high. It stops just as it hits the vacuum plunger. (see pic)
I can push it down very easily, trigger the switch and the wiper door will close.
When I push the wiper down that last .5" there only seems to be back lash. Nothing mechanical or solid holding it up. Almost like there isn't enough force on the arm to push the plunger.

Which brings me to my next question; why do I have a screw in a vacuum line coming off of the wiper plunger?
The wiper door works as advertised using the wiper switch or the over ride switch under the steering column. It holds vacumm after the car is shutoff and I can get 3 or 4 ups & downs of the wiper door.

First pic, wipers at park by turning off wiper switch, wiper arm just touching vacuum plunger (but doessn't seem to have enough umpf to push it down).

Second pic, wipers at park after I push the arm down, tripping the vacuum plunger.

Third pic, vacuum hose to wiper plunger with screw in it. Where should this be going?

Thanks again for all the help,
Mike

[Terry M.]

Re: 70 windshield wiper adjustment?

Take the screw out. That is a vent line that connects to nothing.

Try the wipers with the windshield wet. That would be how you operate them, right?

There is an adjustment procedure for the wipers in the AIM. Get it (the AIM that is) from the folks who sponsor this site. Click ont he button for the NCRS Store, or call during normal business hours the NCRS office in Cincinnati.

[Alan S.]

Re: 70 windshield wiper adjustment?

Hi Mike,
NEW old 70, NICE!!!!
I think you'll find having the 70 Chassis Service Manual, and the 70 AIM (Assembly Instruction Manual) will be a big help, as Terry suggests, as you get to know your car.
In those wiper instructions there's mention of a screw that 'adjusts' the 'sweep' of the wiper arms. That adjustment MAY help your problem if removing the screw in the hose hasn't.
Good Luck!
Regards,
Alan

Here's a picture of the screw.

[Mike F.]

Re: 70 windshield wiper adjustment?

Thanks for all the help. After all the tinkering, cussing and adjusting I figured out the passenger side wiper arm is incorrect for the car.
There isn't an adjustment screw for the arm and after closer examination it doesn't match/mirror the driver side arm.

I'm hoping a new arm will fix the problem.

Thanks again,
Mike

[Jack H.]

Re: 70 windshield wiper adjustment?

Yes, the screw plugging the vent line is a reasonably common prior owner/Bubba modification. It comes from the earlier fella failing to understand that the wiper door's vacuum system had to VENT vac for the wiper door to open, that if the vent stack was left out in the 'open' in the cowl it would suck in airborne moisture, so the vent stack was covered with a rubber tube running into the engine compartment to take advantage of the relative dryness underhood.

Bubba saw this 'unconnected' tube and in his ignorance he plugged it...

[Jack H.]

Re: 70 windshield wiper adjustment?

The RH wiper arm was typically the first to break (plastic clips that held the external washer tube to the wiper arm disintegrated and the rubber tube connecting to the washer tube provided a spring action to drive and fatigue fracture the washer tube)...

Next, you'll find descriptive text in the Chassis Service Manual on the Corvette WSW system (1970 CSM will describe the '69 Corvette because that's what was in production at the time the book went to press). There, you'll see that the screw on the correct/original wiper arm merely allows you to merely fine tune the cant of the wiper blade relative to the wiper arm.

The descriptive text will teach the adjustment for the wiper arm(s) sweep and final rest position is made at the crank arm plate. And, there is some minor adjustment for the position of the wiper door vac switch (when does it first contact the RH wiper arm as the arms park?).