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Digital Thermostat Installation in RV HVAC Systems
Page 3 of 5
TEXT OF ALAN PASKEY'S ARTICLE as FOLLOWS (FOR COLEMAN UNITS)
The wires coming out of the a/c are as follows:
Red = +12 VDC
Blue = -12 VDC
Green = Fan High
Gray = Fan Low
White = Furnace
Yellow = Compressor
The wire terminals on the new stat are as follows:
RC = cooling relay
RH = heating relay
G = Fan
W = Heat
Y = A/C compressor
I hooked up everything as follows:
RC = Red wire
RH = Red wire
G = see notes below
W = White wire
Y = Yellow wire
Notes:
1. I did not use the Blue wire (-12 VDC)... The book says it goes to all relay coils but as far
as I can tell in the stat, it is used for a delay circuit for the compressor... I MAY BE
COMPLETELY WRONG!!! I have the circuit drawn out if there is an EE or someone
smarter than I am that can figure it out... It looks like a simple circuit with 2 caps and a
transistor... If someone knows what it is really for, please let me know...
2. I took a wire from "G" on the stat to the common on a single pole double throw (SPDT)
switch... I wired the fan high and fan low to the switch... This allows me to still control
the high and low of the fan just like the old stat...
3. This has worked for me but I can't make any promises for anyone else... A little research
should be able to determine if it will work for you or not...
4. Total cost: $19.99 +tax for the stat from Wal Mart and $2.99 +tax for the switch from
Radio Shack...
Hope this helps someone else out. - Alan Paskey