I just completed this mod and posted in my build thread, but since the thread is almost 30 pages long I figured I'd make a separate post since I had a hard time finding much info on this prior to diving in.
I wanted to convert from the factory, unit-mounted A/C controls to a single wall-mounted thermostat that would control both the A/C and furnace.
For our Coleman Mach 8 (13.5k btuh) I spent $148 on the following parts -
* Controller #8330-752
* Digital heat/cool t-stat (black) - 9430-3382
* Replacement inside cover - 9430-4552
The new controller came with an evaporator freeze stat. There's already two threaded studs up by the evaporator coil and the kit was supposed to come with wing nuts to attach it, which it didn't......luckily I found two in the shop that fit.
Found that there is a plastic wire way from the A/C metal ceiling frame all the way past the ceiling speaker. Found another wire way running perpendicular across the trailer through the TV antenna adjuster. Unfortunately Jayco just butted them together at a right angle and did not connect them to pass through. I picked up a flexible extension at Home Depot and a drill bit set for it, in about one minute I had the two wire ways connected. Used a long plastic zip tie as a fish tape and pulled the t-stat wire through.
Next drilled a hole in the closet ceiling into the wire way and brought the t-stat wire down into the closet above the header, then across to another hole that allowed me to get into the wall cavity where the factory furnace t-stat was.
Had to pick up 12V +/- to feed the new controller through the t-stat. Found 12V+ right next to the t-stat on the bathroom fan/light circuit. Was able to grab a 12V- from the ground feeding the stereo.
Luckily I was able to pull enough slack from the 120VAC romex to reach the new controller with extending the wire. When I went to disconnect the power wiring I found that the ground wasn't even wired in the nut and there was a nick through the insulation on the neutral wire, so that all got fixed while I was at it.
Ran through all of the functions and everything works perfect. We can run high/low fan only, high/lo A/C with continuous fan, high/lo A/C with fan cycling on/off and heat.