RV Modification

Programmable Digital Thermostat

When I found out that it was possible to install a regular household thermostat into the RV, I knew it would be one of the first mods I would attempt. At first I didn't want to get a programmable model, but the selection available at RONA was very slim. The non-programmable ones were actually more expensive than the programmable ones. This particular one was one of the cheaper ones but it has a bonus of having a humidity display as well as separate temperature and programming displays. In fact, it's much fancier than the digital programmable one I installed in my home 9 years ago!

Update

We sold Tango Hotel in May 2010 and purchased The Bullet. This was one of the first modifications I transfered into the new RV. The wiring was all the same. The only thing that was different was the colour of the wires.

The Bullet - Keystone Premier 31BHPR

Stock Dometic wiring
Stock Dometic wiring

Wire matchups in the Keystone Premier
Wire matchups in the Keystone Premier

Finished. The display is blank because the 2AA batteries have not been installed.
Finished. The display is blank because the 2AA batteries have not been installed.




Tango Hotel - Pacific Coachworks Tango 289BH


Before and After

Stock Duo-Therm By Dometic
Stock Duo-Therm By Dometic


Digital Programmable Thermostat
Digital Programmable Thermostat





Of course, wiring was a little more complex than the 2-wire system I have in the house, but in the end it was quite straightforward once I figured out what was supposed to where. I've read some very good sites explaining how to do the wiring, but a lot of them talked about the colours of particular wires. Unfortunately, their colours didn't correspond to the colours of my wires and even the owner's manual of the new unit failed to explain clearly what "R1", "R2", "W", "Y", or "G" actually stood for.

Here's how I wired mine.

Step 1

Mark original wires

The front panel of the original thermostat simply snaps off. It's nice that each wire connection is clearly labeled and I simply removed them one by one and marked them with some painter's tape I had lying around.
Original wire connections
Original wire connections

Connection Label...
Wire Colour
7.5
RED
COOL
PURPLE
FUR
WHITE
HI FAN
BLUE
FAN
BROWN
GND
GREEN

Step 2

Install new back-cover and connect wires

The new thermostat unit is larger than the old one but it fits in position quite well. The trickiest part was trying to match the old labels with the new ones. Rather than having the very logical names on the Duo-Therm, there were cryptic letters that did not seem to correspond to any of the coloured wires I had. Another search on the net and I got a better explanation than I got in the owner's manual. Here's the final wiring setup:
New Wiring Connections
New Wiring Connections

Original Connection Label, connected to...
New Connection Label
GND
RC & RH (jumpered)
HI FAN
G
FAN
G
COOL (A/C)
Y
FUR (furnace/heat)
W
7.5
Not used

Apparently, connecting both HI FAN and FAN together at "G" makes the fan run at high speed all the time. That doesn't bother me, I'd rather it run as fast as possible to reach the proper temperature. I've seen instructions on the net somewhere if you want to add that extra "High/Low" control.

Step 3

Mount thermostat to back-cover

This particular thermostat requires 2 AA batteries to operate. Once it's snapped into the back-cover the system is ready to use.
Digital programmable thermostat with front panel open.
Digital programmable thermostat with front panel open.