Is this an ev100 controller or the sem transistor controller ?
if an ev 100 does it have field weakening and is the 1A bypass coming in
is it a zx card ? if so the last few programable parameters need to be loaded in reverse sequence or it wont save to the card properly and 1A wont energize..........i could go on and on about this particular hyster GE controller but check these things first, of course the other guys could be right it may just be a bad pot or incorrectly adjusted pot.