first, you want to ensure that you have power the the unit. that means checking at the junction box then at the control. if not you have a wiring issue . if you do, cut power to the unit to keep from getting shocked. now you need to ohm out the tco it is clipped to the control board in the console. if it is open that is the problem, but don't just replace it. there is a kit that should be used. when these were manufactured they crimped the wires and broke some causing an increase in resistance over time blowing the tco.