Hello there,
In the RH position the diff is unlocked, in the centre the diff and transfer box is in neutral.
By moving it to the LH and either forward or back will engage diff lock and (if it is adjusted correctly) turn the diff lock light on.
It has often been found that the mechanism gets seized up by the spillage of soda's , caffienated products etc. on the centre console and over a period of time this causes problems on top of the gear and transfer box selectors, even with cup holders fitted !!! Yes, I have been guilty of this too, leading to removal of the centre console and taking the selector to pieces and lubricating with synthetic grease. So far all is well.
Les Parker
Tech. Support and Parts Specialist
Rovers North Inc.