What can I do to get less wander or “hunting” across the course line, when I have my Century I autopilot coupled to my Garmin 430? I had the autopilot worked on, including a servo overhaul, without much improvement.
On the 430, scroll to the setup page for CDI, etc. Select Manual for range sensitivity (rather than Auto), and select 0.3 (rather than 5) for the manual range value. Then, if your coupler has a Localizer position, use that position rather than Nav or Omni, when you are enroute. See how this works out for your Century I, when coupled to the 430 in GPS mode. My Century IIB will hunt a bit if set up conventionally (Omni on the coupler and Auto/5 miles/enroute in the 430). But if set up as I described, it is rock-solid on course; probably within 20-30 feet either side of the centerline, with no hunting or wander. The Auto and the 5-mile (enroute sensitivity) setting is what the 430 will select for itself, if you don’t do the Manual over-ride. And despite the over-ride, the 430 will still auto-range as you close in on the waypoint. For example, as you pass under 30 miles out, it will auto-range from 0.3 (where you manually set it), up to 1.0 (which is its auto-select for Terminal operations). When on an approach it will auto-range to the 0.3 mile setting. Oddly enough, once you have been in cruise on the manual 0.3 setting, with the autopilot tracking 100% solid, when it auto-switches to the 1.0 range you probably won’t see any adverse effect on tracking.
Please try this before you throw any more money at this. It has worked for several people so far. I did have one Bonanza that worked best when manually set on the 1.0 mile range sensitivity (rather than the 0.3 or 5.0 mile range); the KFC-200 was a bit spastic in cruise when the 430 was set to 0.3 in that particular plane. But it was fine when set to the 1.0 option, which worked vastly better than the 5.0 mile setting.
What it boils down to is that when set as recommended, the AP gets a correction signal sooner; it also gets a correction signal that gets larger faster. My suspicion is that this combination helps the AP respond sooner, which in turn requires a much smaller correction. BTW, even when you are tracking a VOR, you’ll often get better results if you set the selector to Localizer, rather than OMNI or NAV, for the same reasons. Please let me know how you make out. I may put this up on BAC, but I probably won’t if it doesn’t work for you.