TruTrak Vizion 385 installed with Garmin GTN650 and HS43 module.
Was on a long cross country over the weekend and discovered the AP will only hold course, not altitude, gotta be the elevator servo or wiring right - here's the kicker - elevator control still works for fully coupled approaches!
Here's a breakdown:
1. Flying along, I select an altitude and vertical speed, engage AP, course is flown, but no elevator changes or fore/aft stick resistance to manual control.
2. I manually fly to the selected altitude and AP displays the normal "approaching altitude" and "altitude hold" messages but again, no exerts no actual control of elevator, no servo hum or resistance to moving the stick fore and aft - doesn't matter if I select existing altitude or dial in an ascent or descent or even if I just use wing level feature - in cruise flight, not elevator control is exerted by AP.
I thought it was possibly a bad elevator servo or a bad connection to the servo but....
3. When on a RNAV approach, I was somewhat startled when between IAF and FAF, (get glide slope indication from GPS) the AP display switched from ALT HLD to CPLD and the AP controled elevator servo all the way down for a successful fully coupled approach with vertical guidance.
This is 100% repeatable. No AP control of elevator in cruise - but once vertical guidance comes from GPS - boom it works.
So the servo is working - it's just not getting any guidance except when coupled.
I sent an email to TruTrak too