[Fulltiming]

Sorry about the alarm Paul and Jane. If you had a coach with propane, I would say check under the couch to reset the propane detector, but you don't. Do you have a smoke or CO2 detector that could be going off? Mine are not AC powered so they are not affected by turning off a breaker. However, I don't know if the newer coaches have smoke or CO2 detectors with backup AC power like my house is.

Since you say the noise stops when you turn off the breaker for the side outlets, including the refrigerator it is obviously powered by 120 volts. Some refrigerators have an alarm in them but usually it is not a very loud noise. My inverter has an alarm on the remote panel but it chirps rather than screams. If you could get to the plug for the refrigerator, you could use a heavy duty appliance extension cord to temporary run it to another outlet but I doubt you have access to the refrigerator plug itself.

Can't think of anything that would have an alarm that would be 120 volt powered other than the inverter and the refrigerator. Might try ear plugs or sticking toilet paper in your ears and check out the refrigerator and inverter panel as potential alarm sources as it should get louder as you get closer to the source.