Garmin G5 install - autopilot problem

[problematique]

Looking for anyone who has installed the G5 and GAD 29B to hook up to a KAP 140. I'm trying to help brainstorm this issue with my mechanic.
- 2000 Cessna S, KAP140 autopilot originally had no issues. Single Axis only (no alt. hold)
- Installed G5 , GMU 11, and GAD 29B
- Had the autopilot updated and ground tested. Checked out OK
- On the flight home realized activating AP simply banked the plane to the left and holds. It didn't matter if it was set to ROL or HDG.
- Also noted that pushing the NAV button on the KAP140 did nothing. The screen would not change.

So the two anomalies are the update to the KAP140 and the integration of the GAD29B.
Has anyone ran into this issue? Perhaps a bad GAD29B is the cause? Or does this symptom of the A/P steering completely to the left sound like a autopilot issue?

 

[Indiana_Pilot]

If I remember reading right and thinking back to how I connected my Century 1 Auto Pilot to a Garmin 300XL and CDI for heading input.. there are 2 wires.. ones that is +150mv for left and the other +150mv for right.. I had a connection in the wrong pin location and it did the exact same thing.. would only want to go left and stay there.. re-seated the connecter pin and all is good.. you may want to check the leads from the A/P to see if they are indeed connected correctly. (my issue was that the right deviation wire was the only one connected)

 

[problematique]

Thx for the advice, I'll pass it on to the shop. I hope this is the problem!