code 59 - steer motor current not present
possible causes are:
-broken or loose wire from lift amplifier to steer motor
-damaged or defective lift amplifier
-damaged or defective steer motor

even though the dash displays look the same between the yale and hyster trucks the software in them is different and you shouldnt try and interchange them. The displays store certain information pertaining to the truck and could cause more damage to the system programming in the controller(s) or at least display incorrect information. Also since the display mounts directly on the controller board you may have inadvertantly damaged the 32pin plug or pins, i would make sure this is not the case. Anyhow these boards are very sensative to electrostatic charge and you could unknowingly blow one out if your not careful and always use a ground strap or make sure you are grounded to the truck in some fashion when handling them.

Did you get your Hyster fixed? We are having the same problem and have tried everything we can think of so far.