Hi frits,
First try to check all the enable signals concerning the dirve direction and the potentiometer as followings:

X5 = connector ~ 9pins at the tiller head
X6 = connector ~ 42 pins at the controller AS2405F.

X5:4 (or X6:14) = the power supply + 14 VDC for the potentiometer.

X5:3 (or X6:1) = + 14VDC/0 => signals for the fork direction, it must be changed the status when pressing the button in the fork direction.

X5:9 (or X6:7) = + 14VDC/0 => signals for the drive direction, it must be changed the status when pressing the button in the drive direction.


X5:5 (or X6:28) = 0 - 12VDC => signals of the potentiometer. It must be from 1.2 - 2.56 VDC when in Zero position and must be 9.4-10.8 VDC when in max position. If not try to adjust the mechanical position of the potentiomter ?

Try to check and find if some of them abnormal and fix it

Good luck and regds
Nuna