Equipment guide
Water Heater error codes
Codes are manufacturer-specific. Choose the exact brand shown on your equipment.
The official ATIO 910 Service Handbook identifies 031 as incorrect dipswitch settings. This record applies only to the documented 910 / 910 ASME (T-M50 / T-M50 ASME) on-demand water heater.
Official A.O. Smith material describes 1 flash as Low flame signal; the control continues to operate. This guide records the cited product-family scope, safety-reviewed owner checks, and service limits.
The official ATIO 910 Service Handbook identifies 101 as abnormal combustion. This record applies only to the documented 910 / 910 ASME (T-M50 / T-M50 ASME) on-demand water heater.
The official ATIO 910 Service Handbook identifies 111 as ignition failure. This record applies only to the documented 910 / 910 ASME (T-M50 / T-M50 ASME) on-demand water heater.
The official ATIO 910 Service Handbook identifies 121 as flame loss. This record applies only to the documented 910 / 910 ASME (T-M50 / T-M50 ASME) on-demand water heater.
Official A.O. Smith material describes 2 flash as Pressure switch failed closed. This guide records the cited product-family scope, safety-reviewed owner checks, and service limits.
Official A.O. Smith material describes 3 flash as Pressure switch failed open. This guide records the cited product-family scope, safety-reviewed owner checks, and service limits.
The official ATIO 910 Service Handbook identifies 311 as output thermistor fault. This record applies only to the documented 910 / 910 ASME (T-M50 / T-M50 ASME) on-demand water heater.
The official ATIO 910 Service Handbook identifies 321 as inlet thermistor fault. This record applies only to the documented 910 / 910 ASME (T-M50 / T-M50 ASME) on-demand water heater.
The official ATIO 910 Service Handbook identifies 331 as mixing thermistor fault. This record applies only to the documented 910 / 910 ASME (T-M50 / T-M50 ASME) on-demand water heater.
The official ATIO 910 Service Handbook identifies 391 as air-fuel ratio rod failure. This record applies only to the documented 910 / 910 ASME (T-M50 / T-M50 ASME) on-demand water heater.
Official A.O. Smith material describes 4 flash as ECO (Energy Cut Off) limit thermostat temperature limit was exceeded; the main burner is shut off. This guide records the cited product-family scope, safety-reviewed owner checks, and service limits.
The official ATIO 910 Service Handbook identifies 441 as flow sensor fault. This record applies only to the documented 910 / 910 ASME (T-M50 / T-M50 ASME) on-demand water heater.
The official Cyclone MXi BTH 120-500 Series 300/301 Service Handbook identifies 45-0 as upper or lower temperature probe short condition. This record applies only to the documented Cyclone MXi BTH 120-500 Series 300/301 commercial gas water heater.
The official Cyclone MXi BTH 120-500 Series 300/301 Service Handbook identifies 48-0 as upper or lower temperature probe open condition. This record applies only to the documented Cyclone MXi BTH 120-500 Series 300/301 commercial gas water heater.
Official A.O. Smith material describes 5 flash as Flame out of sequence sensed. This guide records the cited product-family scope, safety-reviewed owner checks, and service limits.
The official ATIO 910 Service Handbook identifies 510 as abnormal main gas valve. This record applies only to the documented 910 / 910 ASME (T-M50 / T-M50 ASME) on-demand water heater.
The official ATIO 910 Service Handbook identifies 551 as abnormal solenoid gas valves. This record applies only to the documented 910 / 910 ASME (T-M50 / T-M50 ASME) on-demand water heater.
Official A.O. Smith material describes 6-1 flash as Retry limit exceeded (failed trial for ignition). This guide records the cited product-family scope, safety-reviewed owner checks, and service limits.
Official A.O. Smith material describes 6-2 flash as Recycle limit exceeded: pressure switch/high limit opened. This guide records the cited product-family scope, safety-reviewed owner checks, and service limits.
Official A.O. Smith material describes 6-3 flash as Recycle limit exceeded: flame lost. This guide records the cited product-family scope, safety-reviewed owner checks, and service limits.
Official A.O. Smith material describes 6-4 flash as Recycle limit exceeded: flame out of sequence. This guide records the cited product-family scope, safety-reviewed owner checks, and service limits.
The official ATIO 910 Service Handbook identifies 611 as abnormal fan motor. This record applies only to the documented 910 / 910 ASME (T-M50 / T-M50 ASME) on-demand water heater.
The official ATIO 910 Service Handbook identifies 631 as pump failure. This record applies only to the documented 910 / 910 ASME (T-M50 / T-M50 ASME) on-demand water heater.
The official ATIO 910 Service Handbook identifies 651 as abnormal flow adjustment valve. This record applies only to the documented 910 / 910 ASME (T-M50 / T-M50 ASME) on-demand water heater.
The official ATIO 910 Service Handbook identifies 661 as bypass valve fault. This record applies only to the documented 910 / 910 ASME (T-M50 / T-M50 ASME) on-demand water heater.
The official ATIO 910 Service Handbook identifies 681 as external fan mode failure. This record applies only to the documented 910 / 910 ASME (T-M50 / T-M50 ASME) on-demand water heater.
Official A.O. Smith material describes 7 flash as Flammable Vapor Sensor (FVS) lockout. This guide records the cited product-family scope, safety-reviewed owner checks, and service limits.
The official ATIO 910 Service Handbook identifies 701 as computer board fault. This record applies only to the documented 910 / 910 ASME (T-M50 / T-M50 ASME) on-demand water heater.
The official ATIO 910 Service Handbook identifies 721 as false flame detection. This record applies only to the documented 910 / 910 ASME (T-M50 / T-M50 ASME) on-demand water heater.
The official ATIO 910 Service Handbook identifies 741 as main remote control problem. This record applies only to the documented 910 / 910 ASME (T-M50 / T-M50 ASME) on-demand water heater.
The official ATIO 910 Service Handbook identifies 761 as communication failure. This record applies only to the documented 910 / 910 ASME (T-M50 / T-M50 ASME) on-demand water heater.
Official A.O. Smith material describes 8-1 flash as Flammable Vapor Sensor fault detected. This guide records the cited product-family scope, safety-reviewed owner checks, and service limits.
Official A.O. Smith material describes 8-2 flash as Temperature sensor fault detected. This guide records the cited product-family scope, safety-reviewed owner checks, and service limits.
Official A.O. Smith material describes 8-3 flash as Electronics fault detected. This guide records the cited product-family scope, safety-reviewed owner checks, and service limits.
Official A.O. Smith material describes 8-4 flash as Valve fault detected. This guide records the cited product-family scope, safety-reviewed owner checks, and service limits.
The official ATIO 910 Service Handbook identifies 991 as abnormal combustion. This record applies only to the documented 910 / 910 ASME (T-M50 / T-M50 ASME) on-demand water heater.
The official Cyclone MXi BTH 120-500 Series 300/301 Service Handbook identifies A6-501 as low gas pressure. This record applies only to the documented Cyclone MXi BTH 120-500 Series 300/301 commercial gas water heater.
The official Cyclone MXi BTH 120-500 Series 300/301 Service Handbook identifies A7-1201 as blocked air intake. This record applies only to the documented Cyclone MXi BTH 120-500 Series 300/301 commercial gas water heater.
The official Cyclone MXi BTH 120-500 Series 300/301 Service Handbook identifies A8-1201 as blocked exhaust. This record applies only to the documented Cyclone MXi BTH 120-500 Series 300/301 commercial gas water heater.
The official Cyclone MXi BTH 120-500 Series 300/301 Service Handbook identifies A9-17B as flame sensor detected flame when the gas valve should be off. This record applies only to the documented Cyclone MXi BTH 120-500 Series 300/301 commercial gas water heater.
The official Cyclone MXi BTH 120-500 Series 300/301 Service Handbook identifies B2-70 as ignition failure; flame not detected. This record applies only to the documented Cyclone MXi BTH 120-500 Series 300/301 commercial gas water heater.
The official Cyclone MXi BTH 120-500 Series 300/301 Service Handbook identifies CC-B as powered anode shorted to earth ground or the tank. This record applies only to the documented Cyclone MXi BTH 120-500 Series 300/301 commercial gas water heater.
The official BTR 500 Service Handbook identifies continuous flash as flame sensed out of sequence for more than five seconds without the gas valve being energized. This record applies only to the documented BTR 500 commercial gas water heater with White-Rodgers ignition control.
The official BTR 500 Service Handbook identifies continuous on as internal ignition-control-board failure. This record applies only to the documented BTR 500 commercial gas water heater with White-Rodgers ignition control.
The official Cyclone MXi BTH 120-500 Series 300/301 Service Handbook identifies D6-8 as no water detected by the powered anode. This record applies only to the documented Cyclone MXi BTH 120-500 Series 300/301 commercial gas water heater.
GE Appliances identifies F61 as: Tank water temperature is too hot. This definition is limited to GE Profile GeoSpring hybrid heat-pump water heaters manufactured from June 2025 to current; confirm the complete model number before applying it.
GE Appliances identifies F62 as: Incoming water is too hot. This definition is limited to GE Profile GeoSpring hybrid heat-pump water heaters manufactured from June 2025 to current; confirm the complete model number before applying it.
GE Appliances identifies F73 as: The condensate drain-pan port is clogged. This definition is limited to GE Profile GeoSpring hybrid heat-pump water heaters manufactured from June 2025 to current; confirm the complete model number before applying it.
GE Appliances identifies F74 as: The filter is dirty. This definition is limited to GE Profile GeoSpring hybrid heat-pump water heaters manufactured from June 2025 to current; confirm the complete model number before applying it.
GE Appliances identifies F75 as: Dry-tank fault. This definition is limited to GE Profile GeoSpring hybrid heat-pump water heaters manufactured from June 2025 to current; confirm the complete model number before applying it.
GE Appliances identifies F78 as: The leak sensor detected water. This definition is limited to GE Profile GeoSpring hybrid heat-pump water heaters manufactured from June 2025 to current; confirm the complete model number before applying it.
GE Appliances identifies F81 as: The leak-sensor battery is low. This definition is limited to GE Profile GeoSpring hybrid heat-pump water heaters manufactured from June 2025 to current; confirm the complete model number before applying it.
GE Appliances identifies F96 as: The CTA module is disconnected or its battery is low. This definition is limited to GE Profile GeoSpring hybrid heat-pump water heaters manufactured from June 2025 to current; confirm the complete model number before applying it.
Official Navien material describes E003 as Ignition failure. This guide records the cited product-family scope, safety-reviewed owner checks, and service limits.
Official Navien material describes E004 as False flame detection. This guide records the cited product-family scope, safety-reviewed owner checks, and service limits.
Official Navien material describes E012 as Flame loss. This guide records the cited product-family scope, safety-reviewed owner checks, and service limits.
Official Navien material describes E016 as Overheating of the heat exchanger. This guide records the cited product-family scope, safety-reviewed owner checks, and service limits.
Official Navien material describes E030 as Exhaust overheating - the water heater shuts down when the flue temperature exceeds 149 degrees F (65 degrees C). This guide records the cited product-family scope, safety-reviewed owner checks, and service limits.
Official Navien material describes E046 as Abnormal operation: limit control. This guide records the cited product-family scope, safety-reviewed owner checks, and service limits.
Official Navien material describes E047 as Abnormal operation: exhaust thermostat. This guide records the cited product-family scope, safety-reviewed owner checks, and service limits.
Official Navien material describes E060 as Abnormal operation: dual venturi. This guide records the cited product-family scope, safety-reviewed owner checks, and service limits.
Official Navien material describes E109 as Abnormal operation: fan motor. This guide records the cited product-family scope, safety-reviewed owner checks, and service limits.
Official Navien material describes E110 as Abnormal air pressure. This guide records the cited product-family scope, safety-reviewed owner checks, and service limits.
Official Navien material describes E407 as Hot water outlet: thermistor open or short circuit. This guide records the cited product-family scope, safety-reviewed owner checks, and service limits.
Official Navien material describes E421 as Cold water inlet 1: thermistor open or short circuit. This guide records the cited product-family scope, safety-reviewed owner checks, and service limits.
Official Navien material describes E432 as Cold water inlet 2: thermistor open or short circuit. This guide records the cited product-family scope, safety-reviewed owner checks, and service limits.
Official Navien material describes E434 as Abnormal operation: water adjustment valve. This guide records the cited product-family scope, safety-reviewed owner checks, and service limits.
Official Navien material describes E438 as Abnormal operation: circulation pump. This guide records the cited product-family scope, safety-reviewed owner checks, and service limits.
Official Navien material describes E439 as Abnormal operation: flow sensor. This guide records the cited product-family scope, safety-reviewed owner checks, and service limits.
Official Navien material describes E441 as Hot water inlet 2: thermistor open or short circuit. This guide records the cited product-family scope, safety-reviewed owner checks, and service limits.
Official Navien material describes E445 as Abnormal operation: bypass mixing valve. This guide records the cited product-family scope, safety-reviewed owner checks, and service limits.
Official Navien material describes E515 as Abnormal operation: PCB (printed circuit board). This guide records the cited product-family scope, safety-reviewed owner checks, and service limits.
Official Navien material describes E517 as Abnormal operation: DIP switch setting. This guide records the cited product-family scope, safety-reviewed owner checks, and service limits.
Official Navien material describes E593 as Abnormal operation: front panel key. This guide records the cited product-family scope, safety-reviewed owner checks, and service limits.
Official Navien material describes E615 as Abnormal operation: input and memory. This guide records the cited product-family scope, safety-reviewed owner checks, and service limits.
Official Navien material describes E736 as Abnormal operation: cascade communication. This guide records the cited product-family scope, safety-reviewed owner checks, and service limits.
Official Navien material describes E740 as Abnormal operation: outdoor temperature sensor. This guide records the cited product-family scope, safety-reviewed owner checks, and service limits.
Official Navien material describes E760 as Flushing/service alarm. This guide records the cited product-family scope, safety-reviewed owner checks, and service limits.
Official Navien material describes E782 as Abnormal operation: main panel communication. This guide records the cited product-family scope, safety-reviewed owner checks, and service limits.
Official Navien material describes E785 as Abnormal operation: flow switch/sensor. This guide records the cited product-family scope, safety-reviewed owner checks, and service limits.
Official Rheem material describes 11 as The gas shut-off valve is not fully opened, or gas service has been interrupted. This guide records the cited product-family scope, safety-reviewed owner checks, and service limits.
Official Rheem material describes 12 as LP gas is running low (LP models only). This guide records the cited product-family scope, safety-reviewed owner checks, and service limits.
Official Rheem material describes 14 as Water heater is overheating. This guide records the cited product-family scope, safety-reviewed owner checks, and service limits.
Official Rheem material describes 1L as Water heater has buildup of lime deposits. This guide records the cited product-family scope, safety-reviewed owner checks, and service limits.
Official Rheem material describes 29 as Neutralizer is clogged. This guide records the cited product-family scope, safety-reviewed owner checks, and service limits.
Official Rheem material describes 31 as Faulty inlet thermistor. This guide records the cited product-family scope, safety-reviewed owner checks, and service limits.
Official Rheem material describes 33 as Faulty outlet thermistor. This guide records the cited product-family scope, safety-reviewed owner checks, and service limits.
Official Rheem material describes 61 as Faulty blower motor. This guide records the cited product-family scope, safety-reviewed owner checks, and service limits.
Official Rheem material describes 66 as Faulty bypass motor. This guide records the cited product-family scope, safety-reviewed owner checks, and service limits.
Official Rheem material describes 71 as Solenoid valve circuit failure. This guide records the cited product-family scope, safety-reviewed owner checks, and service limits.
Official Rheem material describes 88 as Reminder of flushing the heat exchanger and/or replacing the water treatment filter. This guide records the cited product-family scope, safety-reviewed owner checks, and service limits.
Official Rheem material describes 90 as Air intake or vent exhaust opening may be blocked; or the vent pipes on the vent termination may not be connected properly. This guide records the cited product-family scope, safety-reviewed owner checks, and service limits.
Official Rheem material describes P1 as Not enough water flow to operate the unit. This guide records the cited product-family scope, safety-reviewed owner checks, and service limits.