Hi Flemming,
The fact that the contractor stays in is a good sign as this indicates the drive circuits are ready. The problem may well then lie in wiring to the direction switches. As you sit on the truck remove the plastic panel on the right of the bulkhead/ dash. The main wiring loom comes up here and there are brown connector plugs. Check all of these plugs for corrosion and use a small screwdriver to open up the pins a little. Tomorrow I will try to find a wiring schematic to send to aid tracing wires back.
Best of luck from windy rainy Britain! :-)