The diverter uses two coils. One to move it left and one to move it right. CHeck the coils in solenoid test to confirm the non-working coil. Check coil for overheating, make sure sleeve is not melted and mechanism moves freely. Check for broken wiring and/or short. If coil overheating and no short then check board connectors for evidence of overheating. Could also be blown fuse or bad transistor.