Yes the venerable king KFC-200is an old autopilot. The disconnect tone stopped alerting. It works fine during the self test on the ground. Any thought on what is going on?
Is your momentary big red disconnect button sticking? It will disconnect on push but won’t sound the tone until you release. If you hold through the normal tone length, you get no disconnect tone at all. I do that to avoid alarms that could upset passengers sometimes.