1972 wiper motor issue

[Phil F.]

The wiper motor on my 72' does not work. I removed it, and I was able to get it to start, rotate the main shaft, and operate the washer pump, on the bench, using jumper wires. The problem is that when installed, nothing operates. I checked the continuity of the firewall switch, which prevents the wipers from starting until the cowl door is fully open. It is good. I have power to the dash wiper switch. I have power from the dash switch to the harness plug, that plugs into the wiper motor. If I run power directly to the "hot lead" of the wiper motor, it runs the main shaft. The only thing I can determine is there must be a problem with the internal relay of the wiper motor. Am I on the right track ? Thanks Phil

[Terry M.]

Re: 1972 wiper motor issue

You may be on the right track, but have you checked the ground at the wiper switch inside the car? It is quite common for the center instrument bezel to break at the narrow points and when this happens the wiper switch can lose its ground. I can not tell you you what the symptoms of a missing ground at the switch are, but based on earlier posts from more than a few members it is the first place I would check if I had any kind of wiper motor problem.

[Paul O.]

Re: 1972 wiper motor issue

Phil

I agree with Terry that one of the first items to check is all the grounds. Corvettes need very good grounds to operate due to the fiberglass body. It also sounds like you do not have voltage problem it sounds like you may have a amperage problem. What I mean by that you have voltage but not enough amperage to do the work till you directly feed the motor.

Corroded terminals, broken wires with a few strands still connected, bad or minimal grounds can all allow voltage but insufficient amps to do the work. So I would also check for those type of problems.

Paul 18046

[Jerod M.]

Re: 1972 wiper motor issue

I think you've already addressed this potential problem with your previous diagnostic efforts, but I just wanted to point out that the dash switch harness plug can be installed upside down.

[Jeffrey S.]

Re: 1972 wiper motor issue

Check the ground at the starter. This is the main ground for the wiper motor if it's the same as in '69 I have had this go bad and the wiper motor would only work with a door open since the motor was grounding through the alarm system. Just another opinion.
Jeff

[Phil F.]

Re: 1972 wiper motor issue

Thanks all for your help. I discovered that the knob under the steering column that is used to stop the wiper blades for service ,was in the "on" position. When I turned it off, the wiper motor came to life. Now, the problem is that when I switch "off" the wiper switch on the dash board, the wiper motor still runs. I have to turn the knob under the steering column "off" to stop the wiper motor. The dash switch still allows two speeds, and the washer function still works. It just seems not the stop the wiper motor in the off position. Phil