Dynamic braking and Light globes for fuses.
A 12 volt 50 headlight watt globe will allow the motor to run at pretty much full speed and also function as a protection device. The inrush current will be high but it can allow you to fault find easier than replacing a bag of fuses.
How many wires go to the motor?
I blew up lots of switching transistors when trying to make an intermittent control for a windscreen wiper on an old car back in student days. It turned out the wiring of the motor placed a dead short across the armature to provide a dynamic brake and park the wiper at the same spot every cycle.
HTH
Brian