gtn750 RNAV+V approach question

[chip5620]

Just wondering how to intercept the glideslope with the gtn750 on an RNAV approach, the autopilot should be capable of shooting an RNAV so I'm assuming I'm doing something incompetent. Also, the autopilot is being finicky with the nav and approach hold and sometimes just starts turning off somewhere with a mind of its own, either that or it won't follow the course (and yes I definitely have the CDI set to GPS). Any advice would be appreciated.

[Taguilo]

Hi,

Are you setting the HDG bug properly, as stated in KAP140 manual?

Tomas