I have a 99 JLG 450A lift that won't move. It was parked for about two weeks and when we went to move it two of the wheels act like the brakes are on. The steering wheels will turn but not the others. It will also only turn the wheels in one direction (Left or Right). I have replaced the steering control in the platform controls (Part#1600287) from JLG. This still did not help. The lower control box had a mouse nest where they chewed thru some wires that were repaired. Any help would be great!
I have the same lift you do. I have performed alot of different repairs to mine when I first bought it. . pull the lever (pictured) back or forth and this will manually move your machine or pull a heavy load on the motor if brakes are not releasing.
The steering is affected by the coils on the valve block on the right side of the machine...IIRC, they're the second set down from the top. If it will steer one way and not the other, you can flip reverse the two coils and find out if it's a coil, the shuttle valve, or a wiring issue. With it not wanting to move, ensure your brakes are receiving 12v like Voodoo said first. The brakes should release once the drive controller is moved forward or reverse, or when the steer is activated.