2004 Hummer H2 windshield wiper motor

Upon arriving in MT with sub freezing temps, my windshield wipers will not make a complete revolution. They only go about 1/4 of the way and stop. If I flip the wipers away from the window, like you do before a snow storm so that the wipers don't get stuck to the windshield, they rotate fine. They when the wipers are put back into there normal position, touching the windshield, they only move 1/4 of the way and stop. Is my wiper motor worn out? Or is there a control module?
Thanks