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A.O. Smith Water Heater Error Codes
Choose the code exactly as shown. Meanings and reset procedures can change across model families, display formats and markets.
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1 flash 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.
Search/display variants: 1 flash, 1flash caution 2 flash 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.
Search/display variants: 2 flash, 2flash caution 3 flash 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.
Search/display variants: 3 flash, 3flash caution 4 flash 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.
Search/display variants: 4 flash, 4flash stop-use 5 flash 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.
Search/display variants: 5 flash, 5flash caution 6-1 flash 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.
Search/display variants: 6-1 flash, 61flash caution 6-2 flash 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.
Search/display variants: 6-2 flash, 62flash caution 6-3 flash 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.
Search/display variants: 6-3 flash, 63flash caution 6-4 flash 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.
Search/display variants: 6-4 flash, 64flash caution 7 flash 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.
Search/display variants: 7 flash, 7flash stop-use 8-1 flash 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.
Search/display variants: 8-1 flash, 81flash stop-use 8-2 flash 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.
Search/display variants: 8-2 flash, 82flash caution 8-3 flash 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.
Search/display variants: 8-3 flash, 83flash caution 8-4 flash 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.
Search/display variants: 8-4 flash, 84flash caution 031 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.
Search/display variants: 031 caution 45-0 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.
Search/display variants: 45-0, 450 caution 48-0 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.
Search/display variants: 48-0, 480 caution 101 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.
Search/display variants: 101 caution 111 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.
Search/display variants: 111 caution 121 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.
Search/display variants: 121 caution 311 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.
Search/display variants: 311 caution 321 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.
Search/display variants: 321 caution 331 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.
Search/display variants: 331 caution 391 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.
Search/display variants: 391 caution 441 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.
Search/display variants: 441 caution 510 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.
Search/display variants: 510 caution 551 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.
Search/display variants: 551 caution 611 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.
Search/display variants: 611 caution 631 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.
Search/display variants: 631 caution 651 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.
Search/display variants: 651 caution 661 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.
Search/display variants: 661 caution 681 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.
Search/display variants: 681 caution 701 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.
Search/display variants: 701 caution 721 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.
Search/display variants: 721 stop-use 741 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.
Search/display variants: 741 caution 761 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.
Search/display variants: 761 caution 991 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.
Search/display variants: 991 caution A6-501 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.
Search/display variants: A6-501, A6501 caution A7-1201 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.
Search/display variants: A7-1201, A71201 caution A8-1201 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.
Search/display variants: A8-1201, A81201 caution A9-17B 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.
Search/display variants: A9-17B, A917B stop-use B2-70 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.
Search/display variants: B2-70, B270 caution CC-B 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.
Search/display variants: CC-B, CCB caution continuous flash 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.
Search/display variants: continuous flash, continuousflash stop-use continuous on 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.
Search/display variants: continuous on, continuouson caution D6-8 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.
Search/display variants: D6-8, D68 caution