Originally Posted by Grumpy
You need to buy a new control box for inside the a/c, a thermostat and thermostat wire. Probably close to $150 +/-. The thermostat would cover both a/c and heat. Your current a/c controls are all 120 volt, the new box changes it to 12 volt which switches the 120 on/off.
This is the easy way to do it. I have a Coleman Mach 3 in my 26BH, and I converted it to use a regular house-style digital thermostat (I hate hearing the fan run when the unit isn't cooling). The conversion box is available for my unit, but I never purchased one - I rewired it myself with solid-state relays. It's not something I would recommend someone do themselves unless they have a very good understanding of high and low voltage electrical systems.
For me, the hardest part was fishing the control wire from the thermostat to the A/C unit.
It's an order of magnitude better for sure - you have much finer control over the actual temperature in the trailer, and with my conversion, I can control either heat or cooling with the flick of a switch.