A distribution center reported that a Clark C20 electric forklift's steering wheel would "lock up" (freeze) when turned to the full right position. The operator had to use force to straighten it.
The technician removed the "Steering Wheel Cap." He checked the "Column Bearing" (the bearing supporting the steering shaft). The bearing races were pitted, and the balls were flat on one side. This damage was caused by the operator repeatedly using the steering wheel to pull themselves into the seat.
However, the "Lock-Up" was a separate issue. He checked the "Orbitrol" (Steering Control Unit) mounted under the floor. The "Pressure Set Screw" (which adjusts the relief valve inside the orbitrol) was over-tightened by a previous mechanic. The over-tightened screw blocked the "Neutral Return Groove" inside the valve spool.
When the steering wheel was turned to the right, the spool moved past the normal travel limit, hitting the relief screw. The hydraulic pressure held the spool in that position, preventing it from returning to center. This locked the rear axle in the turn.
The repair involved replacing the steering column bearing and the steering shaft. On the orbitrol, the set screw was backed off to the factory setting (turns count specified in the manual). The hydraulic system was purged. The steering wheel then turned freely and returned to center automatically.
