The now infamous remote control thermostat installed in 2005 model Montanas was a problem for many members. Here is a link to 18 pages (349 Posts) of discussion related to this POS. Included in the text is the part numbers you will need to upgrade to the Comfort Control Center (CCC) replacement unit and instructions for installation. Back in the day, Dometic was replacing them for no charge. Today it will cost you. But the CCC is a way better thermostat.
https://www.montanaowners.com/forums...ead.php?t=8145