Thanks for the replies. I have checked through manuals
and specs and you are right it is not hydraulic. It is... "a high tensile belt drive and epicyclic gearbox
controlled by an electromagnetic fail-safe clutch".
Yes, it prevents me turning the wheel
even when the autopilot breaker is switched off and autopilot course computer is completely off.
I will try disconnecting the clutch this weekend and try again but I suspect that it may be a mechanical issue but will try a few things.
should I spray lubricant onto the push rod? I am thinking it wouldn't hurt?? One thought I have had is that the linear drive motor
is providing much more force than I am with the wheel so may be overcoming a physically stuck rod???
Will try isolating the clutch though.