A duo therm thermostat (p/n 3105058) was removed because it would not operate the air conditioner/heater in a firan fireside camper. it was knocked loose from the wall damaging it.the thermostat is for use in a six wire system.the camper wiring consists of of two bundles; one bundle of two conductors (red and white wires) and a bundle of four conductors(red,blue,white & green wires).the thermostat also has a high/low fan switch. the camper owner bought a white-rodgers model 300 thermostat to replace the bad duo therm thermostat. the white- rodgers unit can be used in either 4 or 5 wire a/c-heating systems.this unit has 8 terminals.the duo therm t-stat has 6 terminals.so far i've put the 2 wire bundle red wire on the"rh" terminal and the white wire on the"w" terminal. i then hooked the 4 wire bundle as follows;red to"rc" terminal,white to"y"terminal,green to"g"terminal,blue to"a"terminal. tested unit-nothing happened.i went back to the white-rodgers t-stat instructions and then put a jumper between the y and w terminals.the heater now works but only in the cooling position - still no a/c. i am now wondering if the white-rodgers t-stat will work in place of the duo therm unit? (note-the camper owner removed the duo therm t-stat and didn't mark the wires, he then called me after he couldn't get it to work.at one time i wired hugh commercial a/c-heaters at the manufacturer,but this is the first time on a camper for me. i'v e did every thing the white-rodgers instructions said to do). please help if you can. richard b. 06/14/2009

A. Remove the cover of the thermostat.
b. Connect the RED wire from the air conditioner
to the “RC” terminal on the thermostat.
c. Connect the “YELLOW” wire from the air conditioner
to the “Y” terminal on the thermostat.
d. Connect the “BLUE” wire from the air conditioner
to the “H” terminal on the thermostat.
e. Connect the “ORANGE” wire from the air conditioner
to the “G” terminal on the thermostat.
f. Push the thermostat wires into hole in wall and
fill excess hole with insulation.
g. Mount thermostat base to the wall with screws
provided.
h. Check all thermostat wires on base to ensure
they are completely clear of the bimetal coil of
the thermostat. Adjust if necessary.
i. Replace thermostat cover.
If nothing operates on the air conditioner, remove the
return air grille assembly and verify the red, orange, yellow
and blue wires are properly connected (red-to-red,
orange-to-orange, etc.).
Next, disconnect the red wires and check for 12 volt
DC between the red wire from roof section and the orange
or blue wire from roof section. If no voltage received,
refer to Section F2. If voltage is received, the
problem lies with the thermostat or thermostat wires.
Next, disconnect all 4 wires (red, orange, yellow and
blue) from the thermostat. With the thermostat set on
COOL mode, FAN mode set on AUTO and HIGH, and
temperature selector set lower than the room temperature. Check for continuity between terminal RC (red wire)
and terminal G (orange wire); and RC (red wire) and
terminal H (blue wire). If continuity is achieved on each,
proceed with the next step.
Set fan switch to LOW. Continuity should NOT be present
between terminal RC and Terminal H, but present between
the other terminals (Y & G) and terminal RC.
If all of the previous checks are good, the thermostat is
good, do not replace it. If any one of the previous checks
are not correct, replace the thermostat.

I looked everywhere for clarification on this mod
All the tips have RW + RC jumpered with a "BLACK OR GREEN" wire ground going to them....that didn't make any sense electronically to me so I put together a schematic diagram and just installed the mod last night...it works perfectly in cool, heat, fan speeds, everything.
http://burdick.home.digital.net/ke4ozd/RVstat.jpg
RC and RW are unjumpered in mine since each could theoretically have a different power source, otherwise you could be working on one alone and the darn thing energize on you from the other units power source.

This is what you need to do verify first the function of each wires.
using a jumper connect the hot lead to the other side and connect the other one to the other wires,
for example put a jumper to the red hot wire and green this should energized the fan or the blower then tag the green wire for fan. Until you verify the completely the functions of each wires then use the WR manual to cross that will be so simple. Note make sure that you don't put a jumper between red to red or hot wire to hot wire. The WR 300 thermostat is for single stage and doesn't fan a high/low fan switch.

I hope this will help you a lot: please contact me through email if you encounter any problem [email protected]