1970 windshield wiper door
Thread Starter
Cruising
Joined: May 2012
Posts: 14
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1970 windshield wiper door
Hello everyone. I am looking to see if someone knows why on my 1970 SB corvette the windshield wiper door opens on its own everytime I start up the car and stays up ? Other things that are also happening is that when im driving it and im on the gas it stays up but if I take my foot off the excelerator petal and just coast sometimes it drops back down but the second I touch the gas pedal it goes up. (wipers work fine in the on or off position )
I just bought and installed a brand windshield wiper door vacuum switch from corvette central but changing it out didnt fix a thing. When I shut off the car the pressure in the system is then released and I am then manually able to push the door back down to its closed poistion.
any suggestions
thanks
V
I just bought and installed a brand windshield wiper door vacuum switch from corvette central but changing it out didnt fix a thing. When I shut off the car the pressure in the system is then released and I am then manually able to push the door back down to its closed poistion.
any suggestions
thanks
V
Drifting
Joined: Jul 2006
Posts: 1,259
Likes: 154
From: Deplorableville Nebraska
Hello, There are 2 main reasons your wiper door acts the way it does. First would be an inbalance between the 2 vacuum circuits. Those being the actuating and the control circuits. If you have a vacuum leak in the control (switching) circuit and the actuating circuit is vacuum tight the wiper door relay would switch the wiper door to the open position. The other situation would be if the wiper door relay was leaking vacuum (allowing atmosphere) past the seals internally directing atmosphere to the open side of the wiper door actuator.
There are methods to test to isolate the actual problem. Test the relay this way. Remove it and apply vacuum to the small metal port to see if it holds vacuum. Secondly, apply vacuum to the large center port with the bottom port blocked. It should hold vacuum. Also see if you have an original relay. It would have the script "AC SPARK" molded into the body underneath the small metal vacuum port. Originals are rebuildable, others not so much.
There are other possible causes, but these are the most common I see. Curious if the wiper door vacuum switch has white or black plunger also. Let us know.
There are methods to test to isolate the actual problem. Test the relay this way. Remove it and apply vacuum to the small metal port to see if it holds vacuum. Secondly, apply vacuum to the large center port with the bottom port blocked. It should hold vacuum. Also see if you have an original relay. It would have the script "AC SPARK" molded into the body underneath the small metal vacuum port. Originals are rebuildable, others not so much.
There are other possible causes, but these are the most common I see. Curious if the wiper door vacuum switch has white or black plunger also. Let us know.
Is my vette stock?? HAHA
Joined: Oct 2015
Posts: 20,222
Likes: 9,359
From: Im not allowed to tell you
2020 C3 of the Year Finalist - Modified
2020 Corvette of the Year Finalist (performance mods)
2019 C3 of Year Winner (performance mods)
2016 C3 of Year Finalist
Most likely you have a small leak on the operator or control side of you system. The system has 2 sides, the control side and the work side. Vacuum applied to the top of the wiper actuator relay keeps the internal plunger at the top of the controller. turning on the system releases the vacuum and an internal spring forces the plunger to the bottom transferring the work vacuum from the front of the actuator holding it closed to the rear of the actuator forcing it open. So this means you most likely have a leak somewhere between the switch and the actuator relay control port. Easiest thing to do is cut a half inch to one inch off of the hose ends so that they have a good seal. If that doesnt fix it test the wiper arm down switch under the cowl on the passenger side and if thats good test the actuator relay. The arm down switch fails a lot as do the actuator relays but the relay usually fails in the plunger o rings on the work side
Why its doing what you see is your engine vacuum is lower when the motor is under load and higher when you are coasting, that extra vacuum while coasting is more than what is leaking, so it closes
Why its doing what you see is your engine vacuum is lower when the motor is under load and higher when you are coasting, that extra vacuum while coasting is more than what is leaking, so it closes
Is my vette stock?? HAHA
Joined: Oct 2015
Posts: 20,222
Likes: 9,359
From: Im not allowed to tell you
2020 C3 of the Year Finalist - Modified
2020 Corvette of the Year Finalist (performance mods)
2019 C3 of Year Winner (performance mods)
2016 C3 of Year Finalist
IM trying to upload a schematic diagram but cant from my work computer...google 1970 corvette wiper door vacuum diagram and you will see a couple of diagrams from willcox troubleshooting that will help
