Either replace the wiper motor circuit board with a new one from the parts house - notice I said just the circuit board, not the entire wiper motor. Very easy and inexpensive.
Or, more preferably, repair the one you already have, super easy and costs you nothing if you have access to a soldering iron and electronics (non-acid core) solder. The joints where the harness socket attaches to the circuit board get cracks in them over time. The most common one to fail is the closest to the edge of the board, and that's the ground.
Just heat those joints up and add a little fresh solder to get the puddle moving. Stick the board back in there and you'll be good to go for a very long time. And IMO the original board is better than any Chinese replacement you can buy at the parts store.
Richard