Do NOT have that issue, and I fly the C172 Classic all the time, with a lot of PNS50’s GPS & AP use.
In any case, is the operation of the AP, and GNS530 issue ??
The problem comes out if I have the GNS530 mod. I tried to fly smoothly for a two hour flight without it. I noticed that if you switch from VLOC to GPS, clicking on CDI (on GNS) , the aircraft keeps heading. I also noticed that if I turn off the autopilot, it stops “pulling” to one side
OK, I can imagine that happening … under certain circumstances
At what altitude ? Or more to the point, at what Airspeed.
What you describe would match the behaviors of the aircraft at stall or near stall airspeed.
What are
(1) Your air speed
(2) Your altitude
(3) RPM
(4) Flaps
(5) Trim
I suspect one or more of these will be inappropriate, and would indicate why you are having this issue.
- 120 IAS
- 3000/6500ft AMSL
- 2500 (C172) / 2200 (P28R)
- Up
- Untouched
I don’t think the GNS530 is involved here because it doesn’t control the autopilot. Also, you are in HDG mode so there is no connection between the GPS and the autopilot.
But it only happens when I load the GNS mod 
Could you post a short video of this, with enough zoom to read the 530, and AP settings?
Do you also have the G1000 NXi mod installed ?
And/or anorher AP/GPS mod ?
seems a strange situation. ?
You are right of desired course, so you are banking LEFT, as expected.
but
Bank angle is excessive, and your current heading is 060, and the GPS “MESSAGE” is telling to to turn the other way, RIGHT to 111 and your heading bug is set to 111’ish)
I must be missing something ?
Negative. I’m on desired course and airplane bank to left/right as in screenshot
You are banking left, with Gyro compass saying you are passing through a heading 060, Mag Compass says 075 (but you are in a STEEP turn so its not accurate)
Heading bug is about 111, but you are not in heading mode, so irrelevant.
Cannot read what the GTN430 is displaying
Looks to me like the AP is in one of its locked up, unstable modes, from which there is no recovery, apart from re-loading the plane (from Dev Console).
I have had that happen to me on occasions where I have “abused” the AP.
(or I am having a Brain F.a.r.t, and have got that all wrong ? maybe ? )
Despite what the AP says, is it perhaps heading to the VOR the 530 is tuned to? @Cele5899 Did it perhaps end up on bearing 320-330?
My HDG was at 110° but suddenly (when I received the MSG message you see) the plane alone rolled to the left with no bank limit
My advice would be :
If this happens again, or you can reproduce it.
ESC. Turn on Dev Mode. Continue Flying. Re-Load Plane, and see if it fixes the AP.
I cannot see that it is a GNS530 issue ?
OK, then I have no idea … sorry … I have never seen this happen, and I have 100’s of hours in the MSFS C172 Classic.
If I leave the controls it goes into spin and obviously stalls. As if putting the commands all pulled constant to one side without logic
I agree that it doesn’t sound like an issue with the GPS, but probably the AP itself? It’s clearly not doing what it should be doing, that’s for sure.
OK, that is EXACTLY what happens when the AP (for whatever reason) Locks up in some Limit mode.
No idea how that happens in Normal Flight, but sometimes it does.
It also can do this, if you have the AP on when on the ground, or you crash with AP on, (crash detection off), and then slew up and try to fly again.
Not seen anyone come with with any answers yet to this one
Even if you’re using heading nav mode, try to engage GPS with the lighted button on top of panel.
And you didn’t answer my question above…