Lennox F8AUH series Service Manual page 22

COOLING SEQUENCE OF OPERATION
NORMAL COOLING MODE
POWER ON
IGNITION CONTROL MAIN POWER ON.
CONTROL SELF DIAGNOSTIC CHECK.
IS CONTROL OPERATING NORMALLY?
YES
IS POLARITY REVERSED?
NO
ROLLOUT SWITCH MONITORED CONTINUOUSLY.
IS ROLLOUT SWITCH CLOSED?
YES
CHECK FOR MAIN BURNER FLAME SENSE.
IS MAIN BURNER FLAME OFF?
YES
LED: SLOW FLASH RATE REMAINS UNCHANGED
THROUGHOUT COOLING CYCLE.
THERMOSTAT CALLS FOR COOLING.
COMPRESSOR CONTACTOR AND SYSTEM FAN
ENERGIZED WITH 0-SECOND DELAY
(COOLING SPEED). EAC−H TERM. ENERGIZED.
THERMOSTAT OPENS.
COMPRESSOR OFF.
SYSTEM FAN AND ACC. TERM. OFF
WITH 0-SECOND DELAY.
ABNORMAL COOLING MODE
GAS VALVE OFF. COMBUSTION AIR BLOWER OFF.
NO
INDOOR BLOWER OFF WITH NORMAL DELAY.
SIGNAL CIRCUIT BOARD FAILURE AT LED.
INTERRUPT MAIN POWER TO RESET CONTROL.
YES
SIGNAL POLARITY REVERSED AT LED.
NO
GAS VALVE OFF. COMBUSTION AIR BLOWER ON.
SIGNAL ROLL-OUT SWITCH OPEN AT LED.
SEQUENCE HOLDS UNTIL ROLLOUT SWITCH CLOSES.
NO
GAS VALVE OFF. COMBUSTION AIR BLOWER OFF.
INDOOR BLOWER OFF WITH NORMAL DELAY.
SIGNAL UNWANTED FLAME SENSED AT LED.
SEQUENCE HOLDS UNTIL FLAME IS NOT SENSED.
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INDOOR BLOWER ON.