My wipers on my 1991 4.9 when the **** is turned to the left on the lowest setting get stuck mid way the windshield. Brand new wipers. It's happened for a while now. They work fine otherwise but the lowest setting gets stuck. Anyone know why?

 

Stuck as in stopping, but the wiper motor is running or stuck as in an electronic problem?

 

It will go half way up the windshield and quit. And if I take my fist and bump the windshield it most of the time will start working again so it's like it's getting stuck. But it only does it on the lowest setting all the way to the left