66 barracuda variable speed wiper question

There are a few things that result in high motor current. Amx364 has suggested the first, something that is locking the motor. The other is an internal winding short in the fields or armature. The third is an open connection on the fields. Without field current a running motor speeds up and draws excessive current. A stopped motor will not start and draws excessive current. Typically the field is two windings, one on each side of the motor, one is connected to full field the other is fed via variable resistor to vary the speed.

To complicate matters the switch arrangement reverses motor direction for park. For this to happen the polarity of the armature needs to be reversed compared to the field.

The factory service manual has information on how to test the variable motor in forward and reverse by hooking up motor connections to a battery in the correct way for forward and reverse. The manual used to be downloadable from mymopar.com. Section 8-80.

It is much work, but it is best to see if the linkages are free first, then test motor, if it works, then it is likely the switch or wiring. Bench testing is best done by removing motor.