So I replaced my wiper motor with one from an '87 I owned and put it in the '85. The '85 had a busted cover and non-functional motor. The motor I pulled from the '87 worked without a problem before it got wrecked. But in the '85 it acts... strange. Some times when I turn it on, it will sweep a small area and I can hear several clicks and the motor 'flexes' on the firewall a small bit. When pushed down with some force, it clicks and starts sweeping normally until getting stuck again.

Recently I've adjusted the transmission arms and tightened the bolts on the motor-to-firewall (were a little loose). Everything worked fine, then stopped randomly while on LO setting when it rained. So I checked and the sweep starts to gradually slow down on HI to a slow pulse and the motor again is flexing on the firewall. LO and DELAY sometimes work, sometimes do nothing. The only time the motor tries is when washers activate or MIST is held down, afterwards it gets stuck. What I did notice was that the arms would stop in their tracks when set to OFF, and only in MIST did they get low enough to the hood line to set them down. Sometimes when the car ignition is set, the wipers will activate the PARK cycle, and pinching the connector at the voltage test cover will also activate them, if not set.

Then, I removed the arms and kept the linkages on. Now it stays at a constant fast speed, but when the arms go back on, it struggles. I did notice the crank arm for the linkages can be pulled up slightly on the block notch, and when let go, drops back to the original resting position, even if the nut is tight.

Anyone know which component is the culprit?
It seems like too many things are at play at once for me to know what's going on. It's the only thing on this project car that I haven't really figured out yet.

Sorry for the essay.

 

Start investigating with the arms off. There is a park position. When wipers are turned on they sould first go up a few inches, then start sweeping normally. They should not go all the way down to park position while on. When turned off they should go all the way down to the hidden position under the hood.

This schematic is for the 1984 but it is probably the same.