here is a test for the transistor www.forkliftaction.com/forum/thread.asp?trid=19916
make sure the drive motor and cables are good.

there are tests for the power card/system card/regen but way too much for me to list you have to get the service manual if you want to make headway.

this is complex, so if you are not familiar with electronics you might want to hire someone to repair it and express your interest in the matter, he/she may teach you while your paying them. I am willing to help more.