47
Section C - Components, cont’d.
Models 39025.502, 39035.601, 39045.601 & 39045.616
The thermostat is a 24V AC controlled system and is a
bimetal type. It has two switches on the face of the thermo-
stat. On the left side there is a SYSTEM switch and on the
right side there is a FAN switch. This thermostat will oper-
ate an air conditioner and a furnace.
FIG. C48
Verify the thermostat wiring is correct.
A three-conductor cable 18 to 22 AWG is to be used for
low voltage connections. Route low voltage cable from ther-
mostat to unit electrical box. Use .50 dia. snap-bushing for
routing cable into electrical box. See Section C19.
Connect
R
from thermostat to red wire in control compart-
ment. Connect
G
or
F
from thermostat to blue wire in con-
trol box. Connect
Y
from thermostat to yellow wire in con-
trol box. Use wire nuts to ensure good connections.
When connecting a gas furnace to Dometic’s Heat/Cool
thermostat, the
W
and
R
terminals are used. This means
there will be two wires on the
R
terminal (one wire from the
furnace and one wire from the air conditioner).
To check the thermostat, remove all wires. Next, using an
ohm meter with the SYSTEM switch in COOL position and
the FAN switch in AUTO position and the room tempera-
ture above the setpoint temperature, continuity should ex-
ist between
R
to
Y
and
R
to
G
. No continuity should exist
between
R
to
W
. With room temperature below setpoint
temperature, no continuity should exist between
R
to
Y, R
to
W
and
R
to
G
. With the FAN switch to ON position and
the room temperature above the set point temperature con-
tinuity should exist between
R
to
Y
and
R
to
G
. No continu-
ity should exist between
R
to
W
. With the room tempera-
ture below the set point temperature, continuity should ex-
ist between R to G and no continuity between R to Y and R
to W.
With the SYSTEM switch in OFF position and the FAN
switch in AUTO position, no continuity should exist
R
to
Y,
R
to
G
and
R
to
W
. With the FAN switch to ON position,
continuity should exist between
R
to
G
and no continuity
between
R
to
Y
and
R
to
W
regardless of room tempera-
ture.
With the SYSTEM switch in HEAT position, FAN switch in
AUTO and room temperature above setpoint temperature,
no continuity should exist between
R
to
Y, R
to
G
and
R
to
W
. With room temperature below setpoint temperature,
continuity should exist between
R
to
W
and no continuity
between
R
to
Y
and
R
to
G
. With the FAN switch to ON,
continuity should exist between
R
to
G
regardless of room
temperature.
To check ACTIVE terminals, place one lead from the ohm
meter to the
R
terminal and the other lead from the meter
to the ACTIVE (ON) terminal.
SWITCH
COMBINATION
IF ROOM TEMP.
IS ABOVE/BELOW
SETPOINT TEMP.
ABOVE
BELOW
ABOVE
BELOW
ABOVE
BELOW
ABOVE
BELOW
ABOVE
BELOW
ABOVE
BELOW
TERMINALS THAT
ARE “ON”
SYSTEM
SWITCH
FAN
SWITCH
AUTO
ON
AUTO
ON
AUTO
ON
G Y W
X
X
X
X
X
X
X
X
X
X
X
COOL
HEA
T
OFF
Manual
Compliments
of
Northwest
RV
Supply
Printed
From
http://www.nwrvsupply.com
