Service manual link (http://www.tvformyrv.com/template/rv-manuals/Atwood%20Air%20Conditioner%20Service%20Manual%20-%20Rev%2013.pdf)
This is different than the installation manual that ships with Atwood ACs and heat pumps and includes troubleshooting and hidden options, including the user configurable heat pump cutoff temperature which is factory set at 44F but can be dropped down to 32F by entering sensor mode on the thermostat.