1. This modification went very well glad I made it

I carefully read all the info from the various posts on installing a digital thermostat, and then checked out the various thermostats. Long story short - here's the most updated info and what I installed. The Hunter thermostat which many have installed (Model 42996) is supposedly no longer available. Besides, I wanted to REALLY upgrade and put in a fully programmable model which would: 1) be designed to run off batteries if no power is present; 2) fully programmable for workdays and weekends; 3) automatically switch from A/C to Heat when needed for those Spring/Fall days where it is cold in the morning and hot during the day.

I researched both Honeywell and Hunter, and talked to tech support at both companies. Although I liked the features, installation instructions and tech support better at Honeywell, I was not convinced their models would work in an RV installation. In fact, the Honeywell tech support assured me they would not!

So I reluctantly went with Hunter. Researched all the models online, and then went shopping online and at Lowes. Believe it or not, Lowes had the best prices (even better than Amazon), and I bought the Hunter Model 44860 for $59, less my 10% military discount (Good job Lowes!). My research shows this model actually states that it is designed to run on batteries if a power source is not available (i.e. 24v). If you read about this model, you'll quickly discover that the owner's manual and installation SUCKS. In spite of that, it's a great thermostat!

Don't even TRY to buy a small SPST switch and drill a hole in the cover and install it as indicated elsewhere. There is NO room! And I melted the small switch with my soldering pencil (I'm all thumbs when it comes to soldering). So I went shopping at Radio Shack and found a GREAT solution for the high-speed / low-speed fan switch for my DuoTherm setup. You can buy a SPST Rocker Switch, #275-0693 for $3.19. It is brown and has nice big spade terminals. Then buy a package of Insulated, Crimp-on, Quick Disconnects (female spade connectors), #6403049 for $2.19. Easy as pie! Just get about 18″ of small gauge wire (9″ for each lead), use two of the small female crimp-on 1/4″ disconnects (22-16 gauge), cut your 18″ wire in half, crimp a disconnect onto the end of each of the two wires, and plug both wires into the spade terminals on the back of the switch. Then use a small plastic wire nut and connect one of the two wires (doesn't matter which) to the blue (high-speed fan) wire. Connect the other wire to the terminal on the thermostat that has the low-speed fan wire attached to that same terminal.

This switch is nice, since most RVs have the rocker switches. I wanted to be sure that when the rocker is flipped up it is on (like the other switches in my trailer) so I hooked an ohm meter up and when the side of the rocker with the little white dot is pushed in, the switch is “on.” So you can mount it in your wall right below your new thermostat so when you “push the dot” it is in the up position, and it is partially hidden and meets the “WAF” requirements. (Wife Acceptance Factor!)

Just wire the thermostat like the rest of the posts here tell you. No sweat! The biggest challenge is to get the little rocker switch mounted in the trailer wall by spinning on the screw-on nut on the inside of the wall! I was able to stick my fingers into the thermostat wire hole and using two fingers, carefully screw it on while holding the front of the switch with my other hand. I'm warning you - it takes a LITTLE patience!

Everything worked great! Search online for others who have been frustrated with programming this little jewel and you will find posts about how to do it. I'm still learning.

I hope this helps, and anyone wanting to put in a fully programmable thermostat can use this info and not spend hours researching like I did! Plus, if something goes wrong and it doesn't work, just take it back to Lowes for a refund! If this thermostat didn't work, or for those of you who want a programmable thermostat for less money, go to Lowes and buy the Hunter 44110. I'm doing this from memory, but I think it's around $20!

Found out why the low battery is flashing, you have to run plain old AA batteries, and no rechargables, something to do with mercury in the plain batteries?