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I recently purchased a 1971 350 C3 and the wiper door and headlights weren’t working. I tested all components and ended up replacing the headlight switch, both override switches and the wiper door actuator as well as the filter and check valve. Everything worked well afterwards. Today after driving for about 20 minutes the wiper door opened and the wipers started running. The switch was of course off. Cycling the switch did nothing. I stopped the wipers with the override switch by turning it counter clockwise. After the car had been parked about an hour I started the car and switched the override switch back and the wipers stowed and door closed. Any idea what could cause this?
Green wire at the wiper- if JUST it's grounded- the wipers will park
SO some how you are losing a ground on the green wire.
But for them to run they need to see the blue wire grounded.
For them to run at low speed- the green wire must also see a ground.
So just a guess- when the turn on by themselves -Do they run at high speed?
Could be the relay in dash- as when the relay is at rest it's grounding the green wire- the switch controls the relay.
Great info, thank you. I’ll see if I can follow the wire to the relay. I’m not sure if they came on in low or high speed. I’ll pay attention if/when it happens again. Any advice on testing the relay?
Last edited by Rv8driver; Feb 25, 2024 at 12:52 AM.
2020 Corvette of the Year Finalist (performance mods)
2019 C3 of Year Winner (performance mods)
2016 C3 of Year Finalist
I hope you kept the original wiper switch , the repops are complete garbage. I went the same route as you did and my new chinese **** wiper switch failed while I was testing it and adjusting the wipers. Only 4 cycles on and off. I bought and original used switch and it lasted 4 or 5 years from a recycler who used to be a vender here.... Then I found an original new in the box from 68 to replace that one...I think I paid 75 bucks...still works. Dont buy vette supplier chines junk. Headlight switches are about the same quality.... I think I got a decent headlight switch from Lectric limited...good luck with anything electrical switch related
I’ve removed the wiper/washer switch and took it apart, simple switch and the contacts are all good. I removed the relay below the instrument cluster and took it apart as well. It tests normally. I even put some heat on it to see if the contact gap changed since the randomness might be temperature related, things getting hot after driving. Relay seems solid. Somewhere the circuit is getting ground and activating the system. The override switch (electric) can’t open the door so I doubt it’s the problem. Any other ideas?
Somewhere the circuit is getting ground and activating the system. The override switch (electric) can’t open the door so I doubt it’s the problem. Any other ideas?
Behind the tach is a solenoid/vacuum switch. When the dash wiper switch is activated, it triggers the solenoid to change the vacuum to open the wiper door. Once the door is open, an arm in the linkage triggers an electrical switch on the firewall that allows the wiper motor to begin cycling. You may have a wonky solenoid???
2020 Corvette of the Year Finalist (performance mods)
2019 C3 of Year Winner (performance mods)
2016 C3 of Year Finalist
you could have a bad park switch but usually once its parked it should stay there....if it does it again let it run and start moving wires and see if you find on that makes it stop. It most likely would be near a connection or where the wires cross through a bulkhead
I removed the wiper vacuum solenoid from behind the tach, what a PITA. It tests good, holds a vacuum seal until voltage is applied. It’s a sealed unit but should be a simple solenoid winding inside with continuous continuity. Power just activates the solenoid and valve. Don’t see how it could be grounding the system.
2020 Corvette of the Year Finalist (performance mods)
2019 C3 of Year Winner (performance mods)
2016 C3 of Year Finalist
That just controls the wiper door. the relay under the center console is one of the components that turn the dydtem on, the wiper switch sends power there and then controls the speed. You need to find one of Wilcox's old schematics...Do a wiper issues search for a 69-72...plenty here and one might have the schematic you need
I'm leaning back to the main wiper switch on the dash. What you're experiencing is a full-system activation, not just electrical or just vacuum. As I understand it, the body of the switch sees ground by it's contact with the cluster frame. The slider makes an internal connection to that ground path when it activates the system. You could disconnect the plug on the back of the switch and drive around on bumpy roads to see if it's something else that's making the connections activate the system.
The tach solenoid doesn't sound to me like it could be the issue- it just operates the door when it sees a power and a ground.
Before chasing your tail-
Go to the wiper and disconnect just the green wire- turn on the ignition and and the wiper should go to high speed.
Then I'd ground the green wire at the wiper ( not connected to the harness) and then turn on the ignition- move the wiper switch and see if the wipers will only go in the slow speed.
If so- it might be the internal solenoid in the wiper-
I’ll try driving with the wiper switch disconnected, easiest process of elimination. The previous owner ran a ground from the frame of the wiper switch to the frame the switch.
Would a bad wiper motor solenoid be able to activate the door and wipers? The system works normally and stows properly. Then after driving 20 minutes the door opens and the wipers start.
Thanks for the input and tips, I’ll post something when it’s sorted.
2020 Corvette of the Year Finalist (performance mods)
2019 C3 of Year Winner (performance mods)
2016 C3 of Year Finalist
It has to be the switch or the relay. He probably grounded it because the gauge console is broken console and it will loose ground when its broken. I would clean up the relay under that console. It maybe located in the passenger dash on later years
It has to be the switch or the relay. He probably grounded it because the gauge console is broken console and it will loose ground when its broken. I would clean up the relay under that console. It maybe located in the passenger dash on later years
I was thinking the switch not giving a ground signal to the relay-- BUT for the wiper to run-door to open (tach solenoid blue wire is seeing a ground)- the blue wire has to see a ground-and OP hasn't confirmed when it runs on it's own- does it just go to high speed- need to know that to troubleshoot.
The relay under the dash controls the green wire's grounding- so I'm still thinking that- as it has a ground too.
Thank you for the schematic and link, good information. I haven’t had a chance to drive it since I put it back together. For now I left the wiper switch disconnected to see what happens. If they do come on again I’ll pay attention to the speed. I may have a grounding issue because while aiming the headlights they started flickering on and off. The car is new to me and I had not used the headlights before changing the headlight switch which was defective on the air side. No idea if it’s the new switch or an existing issue. I’ll start troubleshooting the headlight wiring today.
Thank you for the schematic and link, good information. I haven’t had a chance to drive it since I put it back together. For now I left the wiper switch disconnected to see what happens. If they do come on again I’ll pay attention to the speed. I may have a grounding issue because while aiming the headlights they started flickering on and off. The car is new to me and I had not used the headlights before changing the headlight switch which was defective on the air side. No idea if it’s the new switch or an existing issue. I’ll start troubleshooting the headlight wiring today.
The repo headlight switch is your problem-it has an internal thermal bi-metal circuit breaker- heats up breaks contact and continues to do that- thank you quality control China.
You can try cleaning up the grounds- contacts on the headlights- but the solution is to replace with an OEM good used switch- run LED headlights- and the best- do a headlight relay set up.
Random wiper operation
