bkm sure sounds like you are on the right track. Only thing I would have done different is to check the switch assembly for simple on-off function to see if that is going to be the issue. You so want to make sure that your brushes are okay and check the resistor which goes to the motor from one of the brush assemblies. One weak spot of these is the plastic switch that is activating the microswitch on the switch assembly. Make sure that it is properly activating.