Good morniing. I have G1 SR22 with a STEC 55X autopilot that is not holding a heading. The trim motor was replaced as it was thought to be the only issue. I have two G5s replacing the Attitude and Heading indicators. The tim works fine with the trim button on the yoke, and the autopilot climbs and decents just fine. My local Cirus service center is stummped. Any advace would be MUCH appreciated.
I had started chasing down issues with my 55x in my G1…and ended up just biting the bullet and putting in a GFC500 with all new servos. And i LOVE IT. Yes it was expensive but since you already have G5s you’re halfway there…sorry, not really an answer to your question but that was my experience.
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Have you checked the turn coordinator?
Ouch… $$$. Thanks for the info. I’ll consider this a last resort.
I have not. Thank you, I’ll give it a look.
I also have a G1 with the STEC 55 and have had several issues, but they have ultimately been traced to problems outside the autopilot box itself. Once it was the turn coordinator and another time it appeared to be a problem with the wiring connections. To trouble shoot (at least for one problem the TC can have) they had me time how long it took to make 360 deg turns in each direction; obviously should be 2 mins and if off significantly might indicate a problem there. Might not diagnose the problem you are having though. WRT the wiring, my AP would intermittently start making a turn or wander off course. AP checked out and the avionics guys went thru the connections, cleaned them and replugged them and the problem hasn’t recurred in the last 2 years. They felt that with the vibration that our airframes have (well, G1’s anyway) in a 20 plus year old airplane that has been known to visit airports near the coast could lead to some oxidation in some of the connectors with resultant poor contact. They said that they didn’t see anything obvious, but again, problem solved. I too was inquiring about replacing it with a digital AP but the avionics guys felt that the 55X was a robust AP even though it might not offer the performance of a digital AP. May or may not have any bearing on your airplane…
Ed,
Thank you for the information. I just got the plane back and plan on taking it to an avionics shop to diagnose the problem. Glad to hear that it’s not just my airplane.
The 55X is likely configured for a KCS 55 compass system, make sure the G5 is appropriately configured. The technician may need to confer with Garmin. I know for sure of a situation where someone’s autopilot wasn’t flying the heading bug correctly and it came down to configuration in the G5.
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I know this answer is going to sound a bit flippant, but I had the same issues and tried to chase them down without a whole lot of success. My problems went away after installing a DFC 90.
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Same here but GFC500…..
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