That switch is simple. Two conductors. Follow the cable down the lift cyl and find the plug, make sure it's fully seated and not damaged. Check operation of the switch with ohm meter. The switch is adjustable and can sometimes loosen up and not be engaged by the mast. It's either closed or open. The truck should slow way down with mast above free lift. The speed that the truck travels above free lift can be adjusted with a handset.
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