'68 Wipers: "Welcome to My Nightmare"

[Russ T.]

Repaired wiper system on a 427-435 4-spd. car using mostly new components and it worked great for ~6 months. Now, wiper door automatically opens when motor is started and wipers work only by using service switch under dash. Vacuum system tests good up to solenoid, but solenoid stays energized (closed) at all times when the battery is connected (even when ignition and wiper switch are both off) thus not allowing vacuum to pass thru and hold wiper door closed. Unplugged electrical connection to solenoid and substantial vacuum will then pass thru, pulling door shut. Ran auxillary ground wire from solenoid to brace under dash with no change. Bench-tested solenoid and found no leaks/probems. A spare one performed the same way.

Wiper motor has good fuse and appears to be grounded properly (checked housing and single black wire). Black cable connecting frame to engine block (near starter) appears grounded (heater blower motor works). Wiper switch is properly grounded. Disconnected 3-wire connector at wiper motor: yellow lead tested hot, lt. blue lead correctly shows ground with switch in lo or high. However lt. green lead fails to show ground when switch is off or set to lo speed like it should. Suspected wiper switch and replaced it with a new spare without success, but can hear it 'click' when it's operated. Again, everything works properly using the service switch under the dash. Any suggestions? Time to unravel harness? Time to sell car?

[Tom S.]

Re: '68 Wipers: "Welcome to My Nightmare"

Russ
Good luck I am pulling my hair out also and didn't have much to start with.I suspect that my problem is partly the arm hitting the relay to quickly, but I don't know how to adjust it. Then they won't go into the park position either.I will get it but may have to take another month long break and work on something else for a while.

Tom Stanto 41491

[Dan M.]

Re: '68 Wipers: "Welcome to My Nightmare"

Russ,

Did you check the metal gauge cluster below the wiper switch to see if it is broken on either side in the thin area below the wiper switch. The wiper switch needs to be grounded to work. In addition the "Vacuum Control Solenoid" mounted on the back of the tack goes to ground via the wipper switch when it is in the LO or HI position. If you get a small shock while touching the upper part of the switch housing while turning off the wipers you have a grounding problem with the switch to the gauge cluster. You may need to use a test light with a 12v source at the clip and use the point to be sure you have a GOOD ground in this critical area.

Dan
ncrs# 35068

[Jim T.]

Re: '68 Wipers: "Welcome to My Nightmare"

Russ the service switch you mention under the dash, if you are referring to the electrical switch with a knob under the dash, this switch is used to stop the windshield wipers on the windshield to clean or replace the wiper blades. It controls the operation of the wipers for this purpose. It has on/off positions and the wipers are supposed to work when it is in the off position.

[Mike Baker]

Re: '68 Wipers: "Welcome to My Nightmare"

Russ,
Have you done anything in the engine compartment that caused you to disconnect the vacuum hoses from the actuator? Were they reconnected incorrectly?

Does the Wiper door open and then close as you start the engine? This would indicate a leak in the vacuum control circut. (white hoses)

There is a quirk somewhere in the '68 electrical system that can cause the wiper system to continue to draw current if the wiper switch is turned on then off while the ignition is off. (this is discussed in the archives). To "reset" the system so that it is not drawing current. Start the engine, turn on the wipers, turn off the wipers, shut off the engine. I disconnected anything in the car that continuosly draws current (such as the clock), added a battery disconnect switch to the negative post on the battery and, used a test light while trouble shooting the wipers.

[Larry E. Howard]

Re: '68 Wipers: "Welcome to My Nightmare"

Russ,
There is one more item to check it your vacuum system mysteriously stops working properly, I have seen it on several C-3 cars that I restored in the past. If the car is parked where mud dobbers can get access they will find the discharge valves in your system and build a nest. This will often stop the function of that part of the vacuum circuit. If you see where they build nests in the bolt holes in the heads or intake you have laying around the garage you can pretty well bet they have found your vent hose. The vent for the wiper system on my 69 is on the vacuum switch on the right wiper you will have to remove the grill and raise the door to access it. This switch has a high failure rate too and if it is faulty will cause the door and the wipers to not work properly. If you haven't changed it you probably should. I used a vacuum source from the engine to bypass the valve and fould it to be the problem. Changed it out and all my wiper problems went away. If I remember correctly, this switch detects the wipers are in the park position and is necessary for both the door and the wiper motor to work correctly.
Good luck!

[Russ T.]

Re: '68 Wipers: "Welcome to My Nightmare"

I diligently searched the archives and found a clue to this problem in a post by Bryan Montford dated 3-10-02. Apparently there is a latch assembly that won't stay in position to keep the solenoid de-energized until the wiper switch is turned on. There's a magnetic switch assembly (called the "magswitch")located in the wiper motor gearbox. When the wipers are turned off, a coil inside the gearbox de-energizes allowing the latch to drop down and open the switch that's completing the circuit to the solenoid. If the latch is slipping off the switch, the solenoid keeps getting current, i.e., stays energized all the time. The magswitch is de-energized when the wiper switch is turned off, dropping the latch into position to put the motor in "park" position. This sounds like my problem. The magswitch is GM P/N 4919647 or P/N 22048273, which I'm sure are both discontinued. I guess it's time to try another wiper motor.
I would like to recommend 3 documents that are indespensible when troubleshooting this system: (1) Chevrolet Dealer Technical Service Bulletin: "1968 Windshield Wiper System, Operation and Diagnosis", dated 3-11-68; (2)Chevrolet Service News: "1968 Corvette Headlamp and Wiper Vacuum Systems and Repairs", dated Sept./Oct. 1967; (3) Dr. Rebuild's "Guide to Troubleshooting Corvette Wiper / Vacuum Systems".

[Tom S.]

Re: '68 Wipers: "Welcome to My Nightmare"

Russ
Thank you for all the info on trouble shooting manuals. I got mine fixed on Saturday with the help of a felow corvette owner. 1. the lines on the relay were hooked up wrong 2. the wires on the switch in the center of the steering column were hooked up wrong. 3. and a small vacuum leak. but having some one to help with was probaly the most important, I had gotten so frustrated with this system I was overlooking some things. We started from the very begining using a diagrahm I had and finnaly got it. Thanks to every one on this board for all your help.

Tom Stanton # 41491