Analog to Digital RV Thermostat Upgrade Mod *Explained*
I swap out my OEM Coleman Mach manual slider type thermostat for a battery-operated Honeywell RTH5100B digital with auto heat and cooling changeover.
I've done this particular upgrade a few times in the past. First I upgraded to a Hunter 42999B and then to a Honeywell Focus Pro 5000 series.
Hunter 42999B -
Honeywell FocusPro 5000 -
The Hunter worked well but didn't have the auto heating to cooling switchover capability, so I changed it to the Focuspro 5000. Unfortunately, the Focus Pro 5000 failed, and I had to in a pinch put the old analog thermostat back in place.
Recently I bought a replacement Honeywell digital, so I decided to video the installation in greater detail than before. I answer some of the questions I've received about the mod and explain operation and wiring.
I've found some confusion has come when RVers try and follow my Coleman Mach wiring when replacing a Dometic Duo Therm. The two companies use slightly different wiring methods. The Honeywell will still work but needs a different hookup. Here is a link to a forum post with photos and a wiring diagram for the Duo Therm upgrade -
Good info and video, Ray. One of the best thing I noticed is the Hunter has a backlit LED. The digital Coleman Mach T-Stat we have in ours doesn’t so this might be a future project. When running wiring for solar I had ours removed so know there is a large hole in the wall. Would you mind posting the overall dimensions of the Hunter T Stat you just installed.
Thanks, It is a Honeywell - Product Size (WxDxH): 4.5 x .75 x 3.5 in.
Thanks Ray! You are the best.
Good information and a great video Ray. I had just purchased a new thermostat for my fifth wheel and was told that the thermostat I purchased would be compatable, as all furnace and air conditioners run of 24V.
I'll have to check the supplied voltage for the thermostat I currently have, glad I watched your video before I broke something!
BTW, I had a Honeywell thermostat in my house in Florida fail, leaving the heat pump/heat strips running full time. Don't know the model, as we are in Missouri, but it looks very similar.
Thanks, Keith. Usually, the 24 volts they refer to is a 24VAC supply that comes off most home furnaces via a step-down transformer. Lets them do long wire runs is the reason I imagine.
RVs don't have that type of voltage to power them. Some people will install a converter to make it happen. I've seen that where an RVer may want to use one of these fancy new Nest thermostats or other WiFi types.
The one that failed on me was the Focus Pro 5000 model TH5110D. It had an intermittent problem where it wouldn't shut the heat off, woke up a few nights with it near 80 in the rig. In test mode, the relays worked OK so think it was an issue with the brain chip.
I decided to give a slightly different model a try this time, it's an RTH5100B
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