Start by checking the wiring coming out the back of the control handle. Those switches in the handle are hard to replace and sometimes break the wire inside of the insulation and is hard to tell its broke. Next go to the relay box to the right check wiring and make sure that both relays work when they are supposed to. last is just make sure your lift lock out box for the BDI is working ok and not cutting out lift because it thinks you have dead battery.