|Slow green flash
||This is normal operation.
|Slow amber flash
||This is normal operation with a call for heat.
|Rapid red flash
||This is a twinning error, incorrect 24V phasing.
||You should check the twinning wiring.
|Four amber flashes
||The control is receiving a "Y" signal from the thermostat without a "G" signal, and this indicates that the thermostat is wired incorrectly.
||You should check the thermostat wiring.
|One red flash
||Flame sensed when there was no call for heat.
||You should check for a leaky or slow closing gas valve.
|Two red flashes
||The pressure switch contacts that are normally open are stuck in the closed position.
||You should check for a faulty pressure switch, miswiring, or an open pressure switch contact that didn't close after the inducer was energized.
|Three red flashes
||Many issues could cause this.
||Check for a faulty inducer, blocked vent pipe, broken pressure switch hose, or a faulty pressure switch.
|Four red flashes
||The contacts on the main limit switch that are normally closed have opened.
||You should check for a dirty filter, an improperly sized duct system, an incorrect blower speed setting, an incorrect firing rate, or a faulty blower motor.
|Five red flashes
||The contacts that are normally closed have opened during the rollout switch. The rollout control is manually reset.
||If it has opened, you should check to see if there's a proper supply of combustion air. Otherwise, you can inspect the inducer's operation, the primary heat exchanger for a sign of failure, or the burner for potential issues. Remember to reset the switch and cycle power to the control.
|Six red flashes
||After the unit began operating, the pressure switch opened four times during the call for heat.
||The furnace will lockout for 1 hour and then restart.
|Seven red flashes
||The flame could not be established. The no-light condition occurred three times during the call for heat before locking out.
||You should check for low gas pressure, a faulty gas valve, a dirty or defective flame sensor, a faulty hot surface ignitor, or the burner for potential issues. The furnace will lockout for 1 hour and then restart.
|Eight red flashes
||The flame has been lost five times during the heating cycle.
||You should check the system for low gas pressure, a dirty or faulty flame sensor, or a defective burner. The furnace will lockout for 1 hour and then restart.
|Nine red flashes
||The line voltage polarity has been reversed or there's a grounding problem.
||You should check the furnace grounding and the polarity at both the furnace and branch.
|Ten red flashes
||A flame has been sensed with no call for heat.
||You should check the gas valve as well as the gas valve wiring.
|Eleven red flashes
||This is usually caused by a failed blower motor or blower wheel.
||After correcting the failure condition, you will want to cycle power to the control which will reset the hard lockout condition.
|Twelve red flashes
||This indicates an open igniter circuit.
||You should check for a disconnected or loose wire, or a cracked or broken igniter.
||This is a control failure.
||You should replace the control board.