ipeltier wrote:
Thanks for all your advice. Once again, the RV Forum comes to our rescue. When I read all your responses to my husband, he did a double check on the battery and reconnected the wires. The squealing stopped. He thinks it might have been a loose connection. But we are also going to check the expiry date on the detector in the morning (not camping in it right now--in a hotel in Great Falls on our way to Arizona).
You know they also make great alarm clocks at 2:00 am in the morning, when the 50 amp has only one good side, and it isn't the one that powers the 12v converter! :S
Glad the solution was easy.