Page 37
G40UH with Ignition Control 78M47 & 100973−01
LED#1 = AN1 LED#2 = AN2
HEATING SEQUENCE OF OPERATION
NORMAL HEATING MODE
ABNORMAL HEATING MODE
CONTROL SELF−CHECK OKAY?
BURNER OFF?
(CONTINUOUS FLAME CHECK)
NORMAL OPERATION:
LED #1 −− SLOW FLASH
LED #2 −− SLOW FLASH
NO
YES
YES
GAS VALVE OFF. COMBUSTION AIR INDUCER OFF.
INDOOR BLOWER DELAY OFF.
LED #1 ON
LED #2 ON
(RESET CONTROL BY TURNING MAIN POWER OFF.)
POLARITY REVERSED.
LED #1 −− FAST FLASH
LED #2 −− SLOW FLASH
POWER ON
IS POLARITY CORRECT?
ROLLOUT SWITCH CLOSED?
THERMOSTAT CALLS FOR HEAT:
LED #1 −− FAST FLASH
LED #2 −− FAST FLASH
IS COMBUSTION AIR
PRESSURE SWITCH OPEN?
GAS VALVE OFF. COMBUSTION AIR INDUCER ON.
INDOOR BLOWER ON.
LED #1 −− ON. LED #2 −− SLOW FLASH.
SEQUENCE HOLDS UNTIL ROLLOUT SWITCH CLOSES
AND POWER IS RESET OR T’STAT IS INTERRUPTED
FOR MINIMUM OF 1 SECOND.
GAS VALVE OFF. COMBUSTION AIR INDUCER ON.
INDOOR BLOWER ON HEATING SPEED.
LED #1 −− SLOW FLASH
LED #2 −− OFF
GAS VALVE OFF.
COMBUSTION AIR INDUCER OFF.
INDOOR BLOWER OFF WITH DELAY.
LED #1 OFF
LED #2 SLOW FLASH
(Sequence holds until pressure switch
opens or thermostat resets control.)
NO
NO
YES
YES
IS VOLTAGE
ABOVE 90 VOLTS?
LED SIGNALS LOW VOLTAGE. CONTROL WILL
NOT RESPOND UNTIL VOLTAGE RISES ABOVE
90 VOLTS.
NO
NO
NO
IS COMBUSTION AIR INDUCER
ENERGIZED?
HAS COMBUSTION AIR PRESSURE
SWITCH CLOSED IN 2.5 MINUTES?
YES
YES
PRESSURE SWITCH IS IN WATCHGUARD MODE.
GAS VALVE OFF. COMBUSTION AIR INDUCER OFF.
INDOOR BLOWER OFF WITH DELAY.
LED #1 −− OFF. LED #2 −− SLOW FLASH.
IS 5-MINUTE RESET PERIOD COMPLETE?
NO
PRIMARY AND SECONDARY LIMIT SWITCH.
CLOSED?
YES
YES
CONTINUED NEXT PAGE
COMBUSTION AIR INDUCER OFF.
INDOOR BLOWER ON
LED #1 SLOW FLASH RATE
LED #2 −− ON
NO
YES
NO
YES
IS THERE A PROPER GROUND?
YES
NO
IMPROPER GROUND.
LED #1 −− ALTERNATING FAST FLASH
LED #2 −− ALTERNATING FAST FLASH
YES
YES
