'64 Wiper Troubleshooting Question

[Scott Butville]

I went through the procedure in the shop manual. The center (brown) wire in the motor plug has power in both accessory and run positions and the ground strap is securely connected and plugged in. I got the motor to run on high speed by pulling the motor plug and directly connecting 12V to the center terminal and grounding terminal #1, just like the manual says. This is supposed to indicate a bad switch. In order to double check, I reconnected the plug to the motor which should give it power and I removed the plug from the switch and grounded the yellow wire that goes to Terminal #1 on the motor. If I understand the circuit correctly, this should be exactly the same thing as I did above, except the motor doesn't run. I verified that both wires (Yellow and Lt Blue)have continuity between the switch plug and the wiper motor plug and also ran an extra temporary ground to the motor case. (I am ignoring the dark blue wire that operates the washer pump to keep things simple.) Since both test hookups appear electrically the same to me, I am stumped as to why one works and one doesn't and would like to get this resolved before just starting to throw parts and money at the problem.

[John H.]

Re: '64 Wiper Troubleshooting Question

In operating mode, the motor functions based on grounding its speed circuits through the wiper switch mounting to the cluster, and the cluster's ground circuit. Doesn't matter what you do to the motor if the wiper switch isn't well-grounded.

[Scott Butville]

Re: '64 Wiper Troubleshooting Question

John, Thanks for taking a shot at my question. Maybe I didn't explain clearly, but taking the speed circuit wires off at the switch and grounding one or both of them with a jumper(s) should eliminate the switch and any ground problems. I'm just trying to make sure the problem is the switch or switch ground. My point is, if I can run the motor by direct hook up to the center terminal and direct grounding of the high speed terminal, why doesn't it work when I supply power and ground one or both speed circuit wires? It seems like I'm doing the same thing! The obvious answer is that there is a break in the speed circuit wire(s) but they check OK for continuity. That's why I'm stuck and need someone to explain the difference. I am a little suspicious because my way of eliminating the switch by grounding the speed circuit wires is much easier than the shop manual's method of direct feeding and grounding the motor once one verifies that the brown wire is feeding power. Maybe the reason they don't suggest that is that it won't work, but I cannot understand why. Thanks again.

[Kenneth S.]

Re: '64 Wiper Troubleshooting Question

I've got a wiring diagram of the mid-year wiper motor. Send me your e-mail address and I will send it to you. kenschurr@bellsouth.net
Ken

[Scott Butville]

Thanks Ken! *NM*

[Scott Butville]

Found the problem

Found the cause of the bizarre test results was that the wiper motor would only run some of the time when direct feeding per the manual. As an aside, the switch operation can also be verified by disconnecting the plug at the wiper motor, turning on ACC power and checking for voltage between the brown power wire and the appropriate terminal or terminals on the plug depending on whether the switch is in the off, low or high position.