Yeznat

I have a 72 that has an issue with the Wiper system.
So first some back ground information, new wiper switch, vacuum lines and new control actuator for the wiper system and light system the headlight vacuum system works fine ...lights on, lights come up , lights off, lights go down so far so good.......as long as it don't rain.

The override system works for both the lights and the wiper door.

With the wiper door in override, open, I can fiddle with the washer switch and get the wiper blades to start to come up and then they go back to park I think I have some thing hooked up *****

I noticed the wiper door came open then closed shortly there after the engine started the first time I started the car in the morning.

this is confusing to me as the wiper system starts electrically, (I think that is) I am not sure I understand how the vacuum and the electric system come together to make it all work.

Any one with a clue or even a good guess I will accept all info and theories

terrys6t8roadster

A non CF vendor sells plastic laminated wiring and vacuum diagrams very reasonable. [In color].The AIM has all the info just harder to decipher. Wilcox has trouble shooting in their tech site that is very helpful. T

East Coast

I'm a newbie here with very little experience but, I had a issue with my wiper system also, It's quite a system to wrap your head around. I searched this forum for related posts, followed a trouble shooting guide, and in the end, found someone pinched a hose during the restore. Located it under the dash next to the tach (wiper door control solenoid).
Did you look at the 3 Port Vacuum Switch under the wiper door? Maybe a simple adjustment of the switch closer to the parked wiper?
All the answers are here on this forum, you just got to weed through the posts. A Vacuum Pump/ Gauge is a must have tool along with patience!
Good Luck, let us know what you find!

Alan 71

Hi Y,
The vacuum portion and electrical portion of the wiper system are intertwined.
The dashboard wiper switch is pushed which sends an electrical signal to the solenoid on the back of the tach to send the vacuum signal to the wiper door relay to signal the wiper door actuator to open the door. When the door is fully open and the linkage on the wiper door mechanism has depressed the button on the wiper door limit switch, THEN the electrical signal is sent to the wiper motor to start the wipers.
This is all to prevent the wiper arms from crashing into an un-opened or partially open wiper door.
Each component must be operating properly, in addition the hoses, both the small 'control' hoses, and the 'large' servo hoses, must be routed correctly.
Your symptom of a 'dancing' wiper door usually means there is a leak on the small "control' hose/relay side of the system.
Do you have a vacuum pump with a vacuum gauge and a trouble shooting guide?
Regards,
Alan

Revi

If the wiper door is open in the override position, the electric wiper motor should work as advertised. If the wipers start to come up and then go back down, you may have an internal issue with the plastic cam inside of the wiper motor. (This is what happened with mine.)
I didn't have any wiper door or vacuum issues, but when I turned on the wipers, the wiper door would open, the wiper arms would come up about 4" and then go back to park. Had the wiper motor rebuilt and haven't had any problems since.

Mashman

The actuator is controled by the relay. When there is vacuum on the control line (small white), then the source (center large yellow) vacuum is dirceted to the down side of the actuator (closest to control line), when vacuum is removed from the control line, then the source vacuum is directed to the up side of the actuator.

When you pull down override it blocks vacuum on the control line. When you turn on the wipers at the switch, power is sent to the solenoid, and it blocks vacuum on the control line. In either case vacuum is blocked on the control line, and the door goes up.

Power does not go to the wiper motor until the door is up, this is controlled by a small switch in the engine bay. Connected to the wiper door linkage is a small rod, when the door goes up, the rod is pushed into the engine bay and pushes a switch, when this switch is pushed, it allows the wiper motor to function. If there is a problem with the linkage, or the switch is bad, the wiper motor will not turn on. This keeps the wipers from turning on unless the wiper door is open.

In order to keep the door from closing until the wipers have parked there is a vacuum safty switch in the wiper bay. The safety switch has a plunger that is pushed when the wipers are parked. If the plunger is not pushed, then safety switch dumps the vacuum on the control line and keeps the door from closing (no vacuum on control line - door stays up). Once the wipers are parked, then the safety switch will allow vacuum on the control line, and the door will do down.

marshal135

I had a new wiper switch too about 2 years old it stopped working got all bound up inside when I tried to switch it into the low position. My wipers would only start to operate then return to park.
I found a new old stop GM orig switch. Problem all gone new switches are just crap.
Marshal

Yeznat

Thanks for the input I do have a mity vac and a schematic as well as the trouble shooting guide I will check the motor, the cam and the switch I will let you know what I find this weekend thanks again for the input.

Revi

Because there are two systems intertwined (vacuum- electric), eliminate one while trouble shooting. With the wiper door open using the bypass **** and the safety switch on the firewall depressed, the electrical portion of the wipers should work just like any other car.
Once you get the electrical portion of the wipers working correctly, then add the vacuum element of the door timing/position, etc..

RAOlds

I have a 78 with wiper issues. Were there 3 different models of wipers (i.e. no delay, interim delay module, final delay module)? Mine interval module looks like a hand wired board that plugged directly into the window fuse position. Help!! Looking for a valid wiring diagram.

Rich Olds

DUB

DEFINITELY a vacuum issue. The vacuum actuator relay for your wiper door is commanding the door to open ...and until the vacuum gets to the small control hose on this relay....it will do this. I have been through this quite often and will give you the time to understand this system and figure it out yourself. Usually this occurs on the headlights..or at least did on a 1970 I restored for a customer with ALL new parts...and found a simple fix that can not be seen.

Make sure that your vacuum check valve is good also.

DUB

vstol

Not trying to jump in here but I have a long L88 hood which eliminates the wiper doors. What do I need to do to bpass the vacum setup to make the motor work? Thanks

DUB

The micro switch that is located on your firewall would need to be jumped so it would be sending the power to the red wire coming out of your wiper motor.

This switch is right behind the right valve cover on the firewall. Make sure that if you jump the connection...make sure you use a gauge wire that is equal to those that are in the connector....do not use a smaller gauge wire.

DUB

vstol

Thanks but that is not an option as you can see with my build site below. Can I trick it at the motor?
https://www.corvetteforum.com/forums...ica-kinda.html

0Willcox Corvette

The limit switch at the firewall is depressed when the door opens. If you don't have the door there is nothing there to depress the plunger.

The vacuum system has very little to do with the motor function aside from this plunger. On a normal car when you turn on the wipers, ground is sent to the tach solenoid on the back of the tach. When this happens vacuum is blocked to the relay and in turn, the actuator pulls the door open. When the door opens the plunger on the door linkage press's on the limit switch, which then allows 12 volts to pass to the motor on the red/white wire.

Willcox

vstol

many thanks

marshal135

DUB,
earlier posting on 10/16 you mentioned a little fix that cannot be seen.
Care to share? I have the same problem with my 68.
At start up the left then right head light doors open followed by the wiper door. This is momentary than they close back up.
I have been looking at this thing till I've become cross eyed.
I have replaced all actuators recently and both relays, 68 has 1 per device only.
When you mentioned the little line on top of the relay was not receiving enough vac prior to the actuator relay activating it made perfect sense.
So if I may know the top secret fix It would be gretly appreciated.
Marshal

DUB

Marshall,
YES and NO.

I hope you understand the amount of hours I spent figuring this out...and it was just not thinking. The research/inquires I invested into verify 'things' that could cause the problem..to take them out of the equation also.

I will ask you this one question....which is what I asked myself...and allowed me to deduce and figure out my quick fix....AFTER all my other research.

WHY are the headlight door(s) and or wiper door opening when you crank it...and then causes them to close???? If you pay VERY CAREFUL attention to the system...and its COMPONENTS...it made complete sense to me so when I did my fix...the problem stopped immediately.

One again....WHY are they raising when you crank it???? WHAT is changing???? What is allowing it to 'self correct'?????? I am about spelling it out for you.

Now...when you spend hours on it and figure it out....you will now covet that information...if not ...put it out on the Internet.

DUB

Yeznat

so a follow up to let all Corvette owners know that it can be done. the spherical Wizard has done it the wipers are fixed and the system works great. Here's what I found first after trouble shooting the system I found the power relay for the wiper motor located under the center console was AJU (All Jacked Up) inside. It wasn't letting the ohms and amps go where they needed so once I found that a simple swap only to find out the switch was also not playing well with the rest of the wiper components, swapped it and viola. move the switch to on , the door opens the wipers come out, they go back and forth until you move the switch to high then they go back and forth faster , and when you set the switch to off the blades Park and the door closes. this stuff cant be made up I tell ya it works .....well there is the issue with not squirting water on the window. I am going to fill the water tank and try it again. but so far so good...... oh yea step one of trouble shooting a electrically controlled vacuum operated door is check the fuses. then the relays and the vacuum , thanks for all the guidance and the support from you guys

Yeznat

oh yea don't swap the hoses to the override switches it makes doors go up when they should'nt