Autopilot navigation with KNS 81

[Villajota]

Hi, If I understand it well, we can use the KNS 81 to navigate in autopilot as long we do not use any GPS device in the aircraft. That is, I can set a RNAV coordinates and a course and the NAV option of the Century will follow the needle.

But I cannot switch the NAV option on. Everything is in place, or so I believe, but NAV cannot be activated. I'm navigating with the RNAV in the old style, that is, correcting direction with HDG.

Any idea?

Thanks,

Jesus