I am not aware of any thing that would cause a beeping noise on the AC units. I would put money it is your smoke detector if you didn't take the batteries out last season. I have forgotten to do that in the past and if it sits all winter after not having the been used and the camper battery removed, the smoke detector battery's will beep. And they can be loud from the outside.
2020 Rockwood Roo 235S
2010 Ford F150 Lariat
Nights Camped in 2021-?
2020-8, 2019-27, 2018-12, 2017-29, 2016-33, 2015-22, 2014-22, 2013-20