So it is moving as fast as a walk? like 3-6mph? If so I do not suspect the controller. Maybe the speed indicator device.... where is yours located? Under the floor, yes, but is it on the driver's side (potentiometer) or on the pass side (MCOR)? (locate the black box thingy)
You will need a digital volt meter with 7 function capability for the next step. Every sparkie owner should have one. They vary in price and quality from $3 to $300
