Thanks for the replies. I think if the motor checks out without shorts or grounds, I'm going to go with replacing the control box. The SEM motor in this unit looks like any other motor so I'm going to take the chance that any problems would be pretty obvious.

If it's an SEM motor (separatly excited motor ) normal testing methods don't show up faults in the motors.

if you've checked the motor itself and found no shorted A1 to A2 and the cables checked out ok then the problem is in the controller itself. This code is triggered by high stall current across the transistors, most cases is from stalling the motor.

this stall code is a dead giveaway when you check the controller code history. I always found it useful to know if the operators were pushing loads or not.

and no this truck is a single motor drive system, the 2nd controller is for hydraulics, it is known as a premium hydraulic control system.
(at least thats what yale used to call it years ago when they first started using the SX controllers in the hyd systems)

in any case though since your not finding any shorted cables and the motor checks ok then you will have to either have this box repaired or replace it with a new one. There are no servicable parts inside this box for the tech. I do believe flight systems has reman box's available.

The fault will probably be in the controller not the motor. Mosfet's get damaged by overloading due to shunting"pushing" and or poor battery condition.also if this is a duel traction motor truck a fault in one controller will cause the other to shutdown

Thanks. I'll run some more tests tomorrow.

Symptom
Control does not operate (line contactor drops out).

Possible Causes and Test Procedures
* Short circuit in armature (terminal A1 to A2).
Disconnect power cables from traction motor terminals
A1 and A2. Check for a short circuit between
the terminals.

* Short circuit of armature terminal A1 or A2 to battery
positive or battery negative.
Disconnect power cables from traction motor terminals
A1 and A2. Check for a short circuit between
each terminal to battery positive and then each terminal
to battery negative.

* Short circuit between power cables to the armature terminals (A1 and A2).
Disconnect power cables from traction motor terminals
A1 and A2. Check for a short circuit between
the power cables.