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2-Stage Furnace & Diagnostic Chart - Atwood 79 Series Service Manual

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WIRING DIAGRAM FOR 2-STAGE FURNACE
DIAGNOSTIC CHART
A diagnostic LED is located inside the exterior access cover
on the outside edge of the horizontal (2) stage control
board. The following graph defines the codes.
An Excalibur 2-Stage furnace must use an
Atwood Digital Thermostat.
Two Stage Furnace
Models 1522 & 2334
WITH DOOR AND WITHOUT DOOR
MOT = Blower Motor
CB = Circuit Breaker
SS = Sail Switch
GND = Ground
LS = Limit Switch
GV = Gas Valve
PS = Power Switch
HV = High Voltage
EL = Electrode
NOTE: The Power Switch (PS)
does not control the air
conditioning system
thermostat function.
Black
Thermostat
Red
MOT
Geen
Blue
C.B.
PS
6
Red
Red
White
White
SS
LS
+ 12
VDC
Blue
Case
Bulk-
Green
head
Yellow
Yellow
–12
VDC
GND
Two Stage Furnace
Model 2540
WITH DOOR AND WITHOUT DOOR
MOT = Blower Motor
CB = Circuit Breaker
SS = Sail Switch
GND = Ground
LS = Limit Switch
GV = Gas Valve
PS = Power Switch
HV = High Voltage
EL = Electrode
NOTE: The Power Switch (PS) does not
control the air conditioning system
thermostat function.
Black
Thermostat
Red
MOT
Geen
Blue
C.B.
PS
Red
Red
White
White
SS
LS
+ 12
VDC
Blue
Case
Bulk-
Green
head
Yellow
–12
VDC
Green
HV
Dual
Cont.
Ignition
Control
5ON-12
5 4
3 2 1
1
2 3 4 5 6
Orange
Blue
Yellow
Red
Brown
Low
Main
Redundant
Valve
Valve
Valve
GV
HV
Dual
Cont.
Ignition
Control
5ON-12
6
5 4
3 2 1
1
2 3 4 5 6
Orange
Blue
Yellow
Red
Brown
Yellow
Low
Main
Redundant
Valve
Valve
Valve
GV
GND
2-Stage Furnace Diagnostics
NUMBER OF LED FLASHES
DIAGNOSTIC INFORMATION
1
Low Input voltage
2
Ignition Failure
3
Open High Limit
4
Stuck Sail Switch
5
Module Fault
: A
lockout is a condition that is timed and will make additional
NOTE
SOFT
attempts to correct the problem. A
the thermostat or turning the power switch off then back on.
MOT = Blower Motor
GND = Ground
SS = Sail Switch
GV = Gas Valve
LS = Limit Switch
HV = High Voltage
PS/CB = Power Switch/
EL = Electrode
Circuit Breaker
NOTE: The Power Switch (PS)
does not control the air
conditioning system
thermostat function.
Thermostat
EL
Red
Geen
Blue
PS/CB
Red
Red
White
LS
+ 12
VDC
Blue
Green
Yellow
–12
VDC
GND = Ground
GV = Gas Valve
HV = High Voltage
EL = Electrode
NOTE: The Power Switch (PS) does not
control the air conditioning system
thermostat function.
Thermostat
EL
Red
Geen
Blue
PS/CB
Red
Red
White
LS
+ 12
VDC
Blue
Green
Yellow
–12
VDC
13
LOCKOUT
SOFT
SOFT
SOFT
HARD
HARD
lockout requires reset of
HARD
Green
Black
Dual
MOT
Cont.
Ignition
Control
5ON-12
6
5 4
3 2 1
1
2 3 4 5 6
Orange
Blue
Yellow
White
Red
Brown
SS
Yellow
Low
Main
Valve
Valve
GV
GND
MOT = Blower Motor
SS = Sail Switch
LS = Limit Switch
PS/CB = Power Switch/Circuit Breaker
Black
Dual
MOT
Cont.
Ignition
Control
5ON-12
6
5 4
3 2 1
1
2 3 4 5 6
Orange
Blue
Yellow
White
Red
Brown
SS
Yellow
Low
Valve
GND
EL
HV
Redundant
Valve
EL
HV
Main
Redundant
Valve
Valve
GV

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