Thanks for your comments.
When i had gone to this truck the engineer had already bypassed the switch with a standard microswitch. I looked like it was simply an on and off position switch.
The strange issue is the truck sometimes works but at slow speed then most of the time it does not work.

This one does not have a zapi or a sauer controller, to be honest i think i have seen something similar to these units on the ac cat counterbalance trucks.

I also think its brake related but cannot proceed any further as i dont have any wiring diagrams/codes etc to help work from.

Thank You for all your comments