There are three fuses for the steps. A main 30 amp. A 15 amp from the ignition that overrides the step switch position by the door when the key is turned on. An another for the switch circuit. Door switches are leaf switches activated by a magnet on the door and make a path to ground. If you have power and get a good ground feeding the controller and you get no power out to the motor the controller is definitely bad. If you install a new controller it should come with a new door switch as it may have a different normal position of open or closed than the one you now have. Be sure to use the new switch or the door will operate in reverse if the switches are wrong.
Mike, RVIA & RVSA Certified Master RV Technician
Amy, Dr. Assistant - Roxie & Mei Ling, four legs each
2000 Gulf Stream Scenic Cruiser 450 hp & 1330# torque
06 Saturn Vue, 06 Chevy Z71 4x4 & 2014 Corvette Z51 M7