'72 Windshield Wipers not working

[Melissa N.]

On my '72 Corvette the wiper door opens when I turn on the wipers but the windshield wipers do not work. The fuse under the dash is good. Any suggestions on the problem and how to fix it? Thanks

[Terry M.]

Re: '72 Windshield Wipers not working

It is common for the knob (large black plastic) under the steering column to inadvertently get turned. This will instantly shut off the wipers wherever they are. In normal operation it is needed to change the holders and/or blade, but when turned during interior cleaning it can lead to exactly your situation. On the other hand there are a lot of other things that can cause the wiper motor not to work, but start there and see if it solves your issue.

[Melissa N.]

Re: '72 Windshield Wipers not working

It is common for the knob (large black plastic) under the steering column to inadvertently get turned. This will instantly shut off the wipers wherever they are. In normal operation it is needed to change the holders and/or blade, but when turned during interior cleaning it can lead to exactly your situation. On the other hand there are a lot of other things that can cause the wiper motor not to work, but start there and see if it solves your issue.

Thanks Terry. I have turned that knob on and off and still the wipers will not move.

[Terry M.]

Re: '72 Windshield Wipers not working

Have you removed the wiper switch recently? Has the Instrument cluster been out recently? Information like this may provide some clue. Did the wipers ever work? Were any repairs made to the car between the time they worked (if they ever did) and the time they didn't work?

The connector on the back of the wiper switch can be installed up-side-down, and will result in no or limited operation of the wipers. If the wiper switch was not removed between the time the wipers worked and didn't work, that is not the problem.

Next thing to try is to be sure you have a ground at the wiper actuating switch. The switch mounts to the top of the instrument cluster and the IC has a designed in weak spot above the instruments and below the wiper switch that is designed to break under pressure in case of an accident. It is so well designed that it often breaks during IC R&R or even normal operation. When it breaks the ground for the wiper switch is often lost, or becomes intermittent. Weird operation of the wiper results. A jumper wire from the birdcage (one can get to it by the bracket that mounts that knob I talked about in the last post) and for the other end of the jumper wire partial removal of the machine screw that goes up into the wiper switch will usually work.

If that is not successful you will need a wiring diagram -- available in your copy of the Chevrolet Service Manual -- and a volt meter to be sure you are getting voltage and grounds to the connector at the wiper motor in order to separate the switch from the wiper motor. If the switch is bad, it can be replaced. If the motor has ceased functioning or the lubricant inside has turned to a solid you will have to decide the limit of your skills as to whether to send it out or try to repair it yourself.

[Jeffrey S.]

Re: '72 Windshield Wipers not working

This may be a real long shot but... does the car have a working alarm? See if the wipers work with the driver or passenger door open. This happened on my car. On my '69 the wiper ground is at the starter motor. If this ground is bad and the car has an alarm, the ground goes through the alarm ground which is piggybacked off the wiper motor ground (at least it is on my '69). With door open the ground is made through the door alarm switch and the wipers work. With the door closed there is no ground and the wiper doesn't work.

The first time this happened to me was the first time I had to get a NY inspection back in 1971. The wipers didn't work and I failed the inspection. I went home to find out why and it was just as Terry suggested- the knob had been turned. I switched it on and went back to get the car re-inspected and it passed.
Jeff

[Melissa N.]

Re: '72 Windshield Wipers not working

Terry--thanks again. The Wipers worked about 3 weeks ago and just stopped working. Nothing was done to the switch or instrument cluster. I will start to go through the rest of your suggestions. I already have the service manual (which I got off Ebay). Thanks again and may be back to you on this. Melissa

[Ralph S.]

Re: '72 Windshield Wipers not working

What about the micro switch on the firewall. is it being pushed in when the wiper door opens?

[Terry M.]

Re: '72 Windshield Wipers not working

What about the micro switch on the firewall. is it being pushed in when the wiper door opens?

Excellent mention Ralph. I had forgotten about that one. The micro switch allows 12 v to the wiper motor when pressed in by the wiper door linkage. If the door isn't opening all the way (linkage corrosion or vacuum actuator failing to move all the way) the micro switch will not fully depress and no 12 volts to the wiper motor.

The round switch under the steering column interrupts the ground for the wiper motor.