Intermittent wipers

i have a 2002 pontiac grand am sometimes the intermittent wipers works properly and sometimes from the park position the wipers move properly 3/4 of the way and then stops and starts a couple of times until they reach the return position then they return properly when the wipers run in low or high they always work correctly what could be problem

The problem might be caused from a defective wiper motor pulse board. The pulse board is what controls all the speeds and modes of the wiper motor. The pulse board is located under the plastic cover on the wiper motor and can be replaced without replacing the entire wiper motor.

Tester