Can't get auto trim to work ...

[JPSchultz]

Once you have it properly wired, check the trim calibration. Mine came programmed in reverse. The autopilot ran the trim backwards as evident by clutch slips and out of trim condition when I disengaged autopilot. I went in to the settings, re-calibrated the trim calibration and it worked beautifully.
SETUP MENU > HARDWARE CALIBRATION > TRIM CALIBRATION

 

[colinrasmussen]

We saw the same thing when it was first set up. Thanks for the reminder.

 

[Mooney231]

I believe all trim servos have a clutch, otherwise the trim wheel would be more difficult to rotate. I'm only familiar with the Century trim servo which can function in two ways: 1- the clutch is engaged by a separate function of the trim switch (for Centry, you push down on the switch to engage the clutch and then pull or push to trim down or up); or 2- the trim motor and clutch are activated by the same movement of the trim switch such as in some Piper installations. This method requires a diode to separate the trim up/trim down from the clutch engagement. I believe the Dynon wiring diagram shows these two possible functions.

Disclaimer: I have not installed the AP yet so not direct experience.

 

[colinrasmussen]

The saga continues. The modified wiring not only did not work, but appears to have cooked the servo clutch. Asked Dynon about this and they asked was the servo a 272C because the wiring diagram works with other Bendix servos, and the C version has to be wired different. My response was, if you knew they were different why didn't you ask me what servo I had. Seems like a simple detail to get right. I love the Dynon system, but pretty disappointed in how this has played out as my avionics shop has wasted about 30 hrs of their time chasing this problem (they haven't charged me) and I now have to install a new servo ($6k), for what could have been completely avoided. Do better Dynon.