I have old hyster which i believe to be an E30b but plate has been removed. have had a lot of problems and repair company have fitted new EV-1 controller but now it is only possible to operate at very slow speed forward or reverse. As soon as motor is subjected to a load then it appears to go to full speed i.e the trucks jerks forward or back, and then lockout cuts in and drive stops. This happens with wheels off ground if brake is applied and pedal is pressed. 1A contactor has been disabled. Repair man is baffled and doesn't know what to check next.
Any suggestions?