Need advise — Aileron trim motor not working with new G3X panel

[MikeinPhoenix]

I’ve just finished installing a new G3X Touch panel which includes new Garmin autopilot servos and have run into a problem I’m unable to resolve. Power for the trim motors comes from the Garmin autopilot servos. The pitch trim motor works fine, however, the roll trim motor doesn’t work. I’ve checked the G3X configuration pages for both the autopilot and trim and don’t see any issues. Additionally, I’ve confirmed there’s power coming from the 2 wire power cable when the control stick buttons are pressed. Lastly, I also confirmed the roll trim servo itself is working ok by using a separate 12v power supply attached to the servo power leads (the servo functioned fine in both directions).

I’ve run out of ideas where to test next and welcome any suggestions.

thanks in advance!

Mike

 

[mburch]

You can rule out an issue with the autopilot servo by simply removing power to it, or even by unplugging it and substituting the Garmin servo removal adapter. Either of these actions will connect the trim switch inputs to the trim motor outputs, bypassing the autopilot servo entirely. If your trim motor still doesn't work, then you have a wiring problem.

I typically also advise people to look at the "Trim Input" indication for the autopilot servo on the System Information page... this will tell you whether the autopilot servo thinks it is seeing trim switch activity.

 

[MikeinPhoenix]

You can rule out an issue with the autopilot servo by simply removing power to it, or even by unplugging it and substituting the Garmin servo removal adapter. Either of these actions will connect the trim switch inputs to the trim motor outputs, bypassing the autopilot servo entirely. If your trim motor still doesn't work, then you have a wiring problem.

I typically also advise people to look at the "Trim Input" indication for the autopilot servo on the System Information page... this will tell you whether the autopilot servo thinks it is seeing trim switch activity.

Matt, I did as you suggested….pulled the circuit breaker for the autopilot servos….and the roll trim motor worked perfectly. Reapplying the power to the autopilot servos and the roll trim motor is dead.

I’ll admit ignorance as I don’t know where this takes me in terms of what causing the issue. Would welcome any suggestions.

Many thanks,

 

[bjdecker]

If you were to look at the LRU Pinouts in the AU revision of the G3X Installation Manual, pages 23-54, 23-55, 23-56 - would there be any differences between what's documented and what you have connected?

 

[MikeinPhoenix]

If you were to look at the LRU Pinouts in the AU revision of the G3X Installation Manual, pages 23-54, 23-55, 23-56 - would there be any differences between what's documented and what you have connected?

Good suggestion…..I just checked wiring against the AU revision and all connections appear good. I was also able to confirm the wiring harness connections and pin placement between the GSA28 and the 507 are all good. I even swapped cable harnesses between the pitch servo and the roll servo and the roll trim motor is still dead when power is applied to the GSA28 . If I pull the GSA28 circuit breaker, the roll trim works just fine. Don’t know if this suggests the brand new GSA28 is bad or something else.

 

[dmattmul]

Good suggestion…..I just checked wiring against the AU revision and all connections appear good. I was also able to confirm the wiring harness connections and pin placement between the GSA28 and the 507 are all good. I even swapped cable harnesses between the pitch servo and the roll servo and the roll trim motor is still dead when power is applied to the GSA28 . If I pull the GSA28 circuit breaker, the roll trim works just fine. Don’t know if this suggests the brand new GSA28 is bad or something else.

Swap GSA28's?

 

[bjdecker]

...Is the strapping correct on each servo?

 

[Richard Connell]

What does the configuration page say?
Can you see the trim inputs operating properly in each servo while in config?
You haven’t enabled the “other” roll trim servo (as in another Garmin servo - not the ray allen one) by any chance? No red trim annunciation on the PFD?

 

[MikeinPhoenix]

Thought I’d provide a final update. It turns out the new GSA28 servo was bad. Even though the LED was showing a “flashing green” indication (which means the servo is correctly talking to the rest of the Garmin system), the unit was bad. Garmin’s customer service folks were very helpful helping diagnosing the issue and felt the servo itself was bad. Garmin sent a replacement and all is good.