I'm going to be using a wiper motor for my toe pincher coffin this year, however, I have wired my wiper motor to my power supply and the motor does not rotate smoothly, instead it seams to tick. I'm using a 12 volt 5 amp power supply and a Jeep CJ5 wiper motor, MN: PPWPM437. I'm baffled as to what is causing this. Any help would be greatly appreciated.