electric step

I'd check the connections from the control box to the switch and on to power. The control box is mounted next to the moter/gearbox in the step. On my model 28, when the switch is on, the white wire is connected to power through a 5 amp fuse. Perhaps there's some moisture in the fuse holder when it rains, or a poor connection that opens when in a moist environment.

You'll need to get the wiring diagrams for your model to determine which wires are for your override switch.