York Furnace troubleshooting: A Guide to common problems & error codes

One Amber Flash: Normal functioning with a system call for cooling.

Two Amber Flashes: Indicates normal operation with a heat request.

Three Amber Flashes: The furnace is operating normally at the end of a heating cycle after satisfying the thermostat setting.

Four Amber Flashes: Airflow restriction is reducing heating capacity. It’s advisable to inspect the air filter or check for dirty filters or closed air registers.

Five Amber Flashes: Points to a restriction in the combustion air or vent system. It’s recommended to examine for any blockages in the vents or issues with the condensate drain.

Rapid Amber Flash: Signifies low flame sense current, necessitating a check of the flame sensor rod for cleanliness and proper placement.

One Red Flash: Detects a flame with no heat demand; potential issues might be a leaky or delayed closing gas valve.

Two Red Flashes: The pressure switch contacts, which should be open, are wrongly stuck closed. This requires checking the pressure switch and wiring.

Three Red Flashes: This could indicate multiple problems such as a malfunctioning inducer, a blocked vent pipe, a broken pressure switch hose, or a faulty pressure switch.

Four Red Flashes: The main auxiliary limit switch, typically closed, has opened. Possible causes include a dirty filter, improper duct sizing, incorrect blower speed, or a malfunctioning blower motor.

Five Red Flashes: Normally closed contacts have opened during the rollout switch operation. Check for proper combustion air supply, inducer operation, primary heat exchanger condition, or burner issues. Reset the switch and cycle power.

Six Red Flashes: Indicates the pressure switch has opened four times during a heating call, leading to a one-hour lockout before a system restart.

Seven Red Flashes: Failure to establish a flame, suggesting potential low gas pressure, a defective gas valve, an unclean or faulty flame sensor, or issues with the hot surface ignitor. This will trigger a one-hour lockout followed by a retry.

Eight Red Flashes: Repeated loss of flame during the heating cycle. Check for low gas pressure, dirty or faulty flame sensors, or burner defects.

Nine Red Flashes: Line voltage polarity has been reversed, or there’s a grounding problem; check furnace grounding and polarity at the furnace and branch.

Ten Red Flashes: A flame sensed without a heat call; requires an inspection of the gas valve and its wiring.

Eleven Red Flashes: Usually caused by a failed blower motor or blower wheel; cycle power to the control after correcting the issue to reset the lockout condition.

Twelve Red Flashes: This code signals an open igniter circuit; look for disconnected or loose wires or a damaged igniter.

Steady Red: This signifies a control failure necessitating control board replacement.