Wiper issues

I have been working a problem for awhile now. I have a 68 Barracuda that when I brought it had a 3 speed/variable motor with a 2 speed switch. The drivers side pivot arm was rusted/frozen. I replaced the pivot arms and installed a new seal kit and lubed all joints. Inspected the motor and found it to be rusted and locked up. Checked the continuity of the switch and found that the high speed side did not pass. I replaced the motor with the same that was reconditioned and works by testing with the procedures in the service manual. I replaced the switch with a NOS 2 speed which I had before. When I tried the wipers they worked for a second and than started to hear a hum from the motor in the off, low and high speed switch positions. No matter what position the switch was in I had a discharge showing on the AMP gauge and motor hum. It appeared as a ground some where to me.
I checked the resistance on all the wires from the firewall connector to the switch and all rang out good. When I tested the motor again by the service manual it all runs smooth and free.
I am stumped. I do not know what originally came with the car as it does not have the fender tag and I do not have the build sheet. I am wondering if the 2 speed switch is compatible with the 3 speed/variable motor. From all the wiring diagrams I have looked at it appears that they are. Anyone ever had this problem?

I would guess no. I've never had these systems side by side. My standard answers for wipers is the correct (or close as you can get) FACTORY shop manual, which you can download free at MyMopar.

And the "Passion" site

http://www.passion4mopars.com/

67Dart273,
Thank you, very informative site. I sent them an email to see if they can help.

they are not compatible. 3 speed motor runs weird, if at all, with 2 speed switch. I installed a variable switch and the problem was resolved.
3-speed/variable motor uses 4 wires, while the 2 speed only uses 3.