29
12. The circulating air blower will continue to run for the
selected Blower Off Delay(P5). This may be 60, 90,
or 120 seconds depending on the Jumper setting on
the Furnace Control Board.
Cooling Cycle
1. The thermostat calls for cooling by energizing the
Y/Y2
or
Y1
terminal with 24VAC.
2. The control energizes the blower in the cooling speed
and sends 24VAC to the contactor in the condensing
unit.
3. When the thermostat removes the call for cooling,
the contactor in the outdoor condensing unit is de-
energized and the control continues to run the fan for
a period of 60 seconds.
Table 7. Motor Control Board Fault Conditions
Diagnostic Description
Green
LED
Red
LED
Fixed
Speed
Furnaces
Control Fault (No Power)
Off
Off
Normal Operation
On
On
Motor Fault
On
Flash
Twin Fault (no motor fault)
Flash
On
Communications Fault
Flash
Flash
Variable
Speed
Furnaces
Control Fault (No Power)
Off
Off
Normal Operation
On
On
Motor Fault
On
Flash
Communications Fault
Flash
Flash
TROUBLESHOOTING
If the furnace fails to operate check the following:
• Is the thermostat operating properly?
• Are the blower compartment door(s) in place?
• Is the furnace disconnect closed?
• Has the circuit breaker tripped or the control board
fuse burned open?
• Is the gas turned on?
• Are any manual reset switches open?
• Is the fi lter dirty or plugged?
• Is the fl ame sensor coated? (Remove and clean
with steel wool.
Do not use emery cloth or
sandpaper!)
• Is there blockage in the condensate drain switch?
Also verify that there is no double trapping of
condensate.
• Is the secondary heat exchanger free of debris and
clogs?
• Is evaporator coil clean and free of debris
(If applicable).
• Are all the LED’s on the furnace and motor control
boards constantly ON? If not, refer to Tables 6 - 7 to
determine fault condition.
IMPORTANT NOTE: The furnace will lock out after 5
failed attempts for ignition and will try again every
hour if the call for heat remains.
• If the Inducer Blower is operating, and items above
have been verifi ed, check the Blower Limit Switch
(Figure 40 or 41, page 51) and reset if necessary.
• If the furnace operates when the Blower Limit Switch is
reset, contact a qualifi ed service technician to identify
and repair the problem.
• If the furnace still doesn’t operate, check the Flame
Roll-out Switches (Figure 40 or 41) and reset if
necessary.
• If the furnace operates when the Flame Rollout Switch
is reset, contact a qualifi ed service technician to identify
and repair the problem.
Fan Mode
• When the thermostat energizes the
G
terminal for
continuous fan (without calling for heat or cooling), the
indoor fan is energized on the selected FAN speed.
• If a call for cooling occurs during continuous fan, the
blower will switch over to the selected COOL speed.
• If the
W
terminal receives a call for heat during continuous
fan, the blower will de energize.
• A call for fan is ignored while in lockout.
• The blower will operate at 50% of the selected high
cooling speed for continuous fan operation.
Diagnostic Description
Green LED
Red LED
Control Fault (No Power)
Off
Off
L1/Neutral Polarity Fault
Flash
Flash
1 Hour Lockout
Alternating Flash
Normal Operation
On
On
Pressure Switch Closed Fault
On
Flash
Pressure Switch Open Fault
Flash
On
Open Limit Switch Fault
Flash
Off
Motor Fault
On
Off
Diagnostic Description
Yellow LED
Low Flame Sensor Signal
Continuous Flash
Flame Present
On
Table 6. Furnace Control Board Fault Conditions
