The way to begin a trouble shoot for a fairly simple problem, is to isolate the motor from everything presently connected to it. This is the quickest way to make progress without a bunch of guessing. Run a NEW temporary wire with a NEW proper amp inline fuse from the battery to the motor terminal. Again be sure you have the proper fuse. It would be nice to eliminate the switch during the test also. The result will be:
1. Wiper won't move
2. Fuse blows immediately
3. Mechanical problem as Brad Allen said. Sticking arms. Linkage interference with something. Fuse blows.
4. Smoke
5. Works good
Be sure you are ready to observe, when power is applied during the test, to see if wiper moves freely and how long it moves before fail. And any other anomalies.
Answer all of these questions:
Do you realize this is a 12V motor?
Can you post the wiring instructions so I can tell you how to wire the test?
Is this a one speed motor or ? How many wires does it have?
Chances are the motor is grounded by bolting to truck and using the chassis metal, like everything else does.
Who installed the motor and who wired it up?
