My airplane just came out of an avionics upgrade that includes a G5 HSI with GMU-11, GAD-29B plus a GTN 650 and unfortunately the G5 heading bug does not drive the Century 21 autopilot correctly. In GPSS mode the AP follows the DTK nicely. I will be calling the shop in the morning to have them fix it, but I was wondering if you guys had any ideas? I will also be checking the 650 and G5 config settings. When in HDG bug mode: 1. moving the heading bug left or right of the mag heading does not turn the yoke unless you go left of right of a totally different arbitrary bearing. (HSI heading does match wet compass) 2. the arbitrary bearing changes when I activate different flight plans/DTKs (in HDG bug mode!, not GPSS) There really isn't a lot of wiring as shown below.