installing digital t-stat help needed

If your new one is for residential use, it probably won't work in the RV.

Residential models work on 24V AC/DC from the furnace controller.
RV units work off the 12 V supply.

Sam Spade wrote:
If your new one is for residential use, it probably won't work in the RV.

Residential models work on 24V AC/DC from the furnace controller.
RV units work off the 12 V supply.

Yea, that's what Shawn from India said when I called the 1-800#. But they will work off 12v. Did some searching on the web, found out you do not hook the blue ground wire up. But still could not get anything to work. Did some reading, tried hooking the red hot wire to the blower motor wire, nothing, tried the heat and a/c nothing, could hear relays clicking but nothing worked. Happened to look up at my volt meter plugged into an outlet and noticed it was on 0. Plugged the shore power in, and now everything works perfect. LOL.

It's a Beautiful Thing! Congratulations! Really, no kiddin', many won't even consider taking that wonderful upgrade on as DIY.

j-d wrote:
It's a Beautiful Thing! Congratulations! Really, no kiddin', many won't even consider taking that wonderful upgrade on as DIY.

Had it not been for not hooking up the shore power, I would of been done in 2 hours or less. It is an easy, cheap upgrade.

Yes you need shore power for th A/C Unit to work but furnace should work directly from battery


Many 'residential digital t-stats' can be used in an RV.

Hunter, Honeywell, LUX are just a few.

Depending on how RV A/C-Furnace controls are set up some don't use the 'Blue Wire' (12V -) and some don't use the 'Red Wire' (12V +)
Wires not used should be taped off and safely tucked inside t-stat panel (don't lose them back inside wall---might need in future)

A/C Fan wiring-----you can install a mini toggle switch to switch speeds from high to low, some can be wired just with Hi Speed wire or LO speed wire, some need both wires connected in order for just HI Speed.

But residential t-stats can be used in RVs------just need to use ones that operate the display using AA batteries

Yes, the heater does work off the house batteries, but if you forget to turn the coach batteries on or forget to hook the shore power back up, because you disconnected everything before messing with the wires. Then nothing works. My simple mistake, just had to laugh at myself.

I did this as my first mod. using THIS tutorial. I have a comment on this page as "Wishbone" with some solutions to my confusion.

The main issues that caused confusion were:
1) The entire thing is powered by the backup batteries, which I have to replace every year. It normally takes 24v, which we have no access to in the RV.
2) It took me awhile to figure out that the furnace and A/C is triggered by ground, not power .. So you feed the green (GND) wire into the RC terminal, not the red one.

Also, another thing that confused me is that the AC only worked sometimes when I installed it. Turns out that for some protection reason, if you turn on the A/C, the thermostat prevents it from turning back on after a waiting period. This is sometimes configurable.

Wishbone51 wrote:
I did this as my first mod. using THIS tutorial. I have a comment on this page as "Wishbone" with some solutions to my confusion.

The main issues that caused confusion were:
1) The entire thing is powered by the backup batteries, which I have to replace every year. It normally takes 24v, which we have no access to in the RV.
2) It took me awhile to figure out that the furnace and A/C is triggered by ground, not power .. So you feed the green (GND) wire into the RC terminal, not the red one.

Also, another thing that confused me is that the AC only worked sometimes when I installed it. Turns out that for some protection reason, if you turn on the A/C, the thermostat prevents it from turning back on after a waiting period. This is sometimes configurable.

The Green wire to RC works on YOUR system....but not ALL
OPs uses the RED (+) to RC and Green is for his Fan Speed

Different systems...different wiring schemes.

A/C Compressor re-start delay is so pressure can equalize and protect motor from starting under a high load

I am using the option for the 5 min delay on compressor start up, seems like a safe move. you can turn that feature off. I did not install a switch so I can have low or high fan speeds, wired it so its on high all the time with the green wire. The grey wire for low is taped up so if I decide to install the switch later its right behind the t-stat.

kwplot34 wrote:
Plugged the shore power in, and now everything works perfect. LOL.

Maybe not.

Having the AC power on will give you the 24V from the furnace/AC controller board probably.

If your heat is supposed to work when on battery power only, that might NOT work still.

(Oops. I see this has been answered already.)