Bet the wiring is the same then. I'd flip flop the batteries if it works 12v you got a bad battery. If that doesn't work flip the wiring on the 12/24v switch. If it runs when the switch says 12v, you have a bad switch on the 24v side. The rest of the wiring appears to all be common to the 12 and 24 volt side, so I would guess that there is no problem in that.