A. O. Smith Water Heater Error Codes — Meanings, Causes & Repair in Greater Vancouver

Seeing a fault code on your A. O. Smith water heater? This guide explains what the most common A. O. Smith water heater error codes mean, what’s safe to check yourself, and when to call HeatLand’s licensed, TSBC-certified gas technicians for A. O. Smith water heater repair across Metro Vancouver and the Fraser Valley.

The codes below apply across common A. O. Smith models (ProLine, Voltex, Signature). Meanings follow A. O. Smith’s documented fault codes — always confirm against your unit’s own manual, because exact wording can vary by model, control board and firmware.

How to read A. O. Smith water heater error codes

Atmospheric/power-vent gas models with electronic-ignition gas controls report faults as a green/red status-light (LED) blink pattern at the gas control valve: count the flashes in each group, then a ~3-second pause repeats the cycle. Voltex heat-pump/hybrid models show short alphanumeric codes (ICE, HPO, EUC, ELC, SF, ECF, E10-E61, Edr, EPL, EDH, ERROR 0-9) on the electronic user-interface display. Flash-to-meaning maps differ slightly between gas-control generations (e.g., Honeywell/Robertshaw); always confirm against the diagnostic label on the specific unit's gas valve.

A. O. Smith water heater error codes & what they mean

These are the A. O. Smith water heater codes our Greater Vancouver technicians see most. Anything marked pro repair involves gas, electrical, sealed-combustion or control-board work that must be done by a licensed gas technician (TSBC-certified in BC) — never open gas or electrical components yourself.

Code	What it usually means	Common causes	Safe to check yourself
LED off (0 flashes)	Pilot/burner not lit, control off, or thermopile has not yet reached operating temperature; on power-vent units can mean no call for heat with power present DIY-checkable	pilot extinguished or never lit; thermopile cold / not generating yet; no gas supply	confirm the gas supply valve to the heater is in the ON position; follow the lighting-instruction label to relight the pilot once; confirm nothing is blocking air intake around the base of the heater
Red light on, solid (no flash)	Pilot was recently extinguished and the thermopile is cooling down; relighting requires the mandatory wait period DIY-checkable	pilot just went out; control turned OFF moments ago	turn the gas control knob to OFF and wait the full 10 minutes stated on the label before relighting once; confirm the temperature dial is at the desired setting
1 flash (every 3 seconds)	Normal operation / heartbeat. No fault present DIY-checkable	unit operating normally	no action needed; this is the normal status indication
2 flashes	Thermopile output voltage low: pilot is lit but the thermopile is not producing the required voltage (commonly a weak pilot flame or a failing/loose thermopile) pro repair	defective or weakening thermopile; weak/dirty pilot flame; loose thermopile wiring connection	confirm the gas supply is fully ON; turn the control OFF, wait the labeled time, and relight the pilot once to see if a stronger flame clears the code
4 flashes	Temperature exceeded limit / Energy Cut-Off (ECO) activated on this control generation: water temperature rose above the safety limit and the control locked out pro repair	thermostat/gas-control valve fault calling for heat continuously; stuck/failed temperature sensing element; energy cut-off (ECO) tripped	confirm the temperature dial is not set excessively high; do not attempt internal repairs; turn the gas control to OFF and arrange service
5 flashes	Temperature sensor failure: the control has detected a fault in the water-temperature sensor circuit pro repair	failed integral temperature sensor; internal gas-control valve fault	confirm the temperature dial setting; turn the gas control to OFF and arrange service (sensor is internal to the control valve)
7 flashes	Internal control failure: the gas control valve / control board has an internal fault and must be replaced pro repair	internal electronics failure of the gas control valve	turn the gas control to OFF and the gas supply OFF, then arrange replacement of the gas control valve by a licensed technician
8 flashes	Power-off failure: the control detects flame/output when it is commanded OFF (gas valve not closing), a safety-relevant fault pro repair	gas control valve failing to shut off; internal control fault	turn the manual gas supply shutoff to the heater OFF and arrange immediate service; do not operate the heater
3 flashes (alternate control generations)	Over-temperature / Energy Cut-Off (ECO) tripped on certain A. O. Smith gas-control generations. On other (Honeywell-type) controls the same condition is shown as 4 flashes – always read the diagnostic label on the specific gas valve pro repair	ECO tripped from over-temperature; blocked combustion air / thermal switch interaction; thermostat/gas-control fault	confirm the temperature dial is not set too high; confirm air intake around the heater base is unobstructed; turn the gas control OFF and arrange service rather than resetting repeatedly
6 flashes (alternate control generations)	Over-temperature / Energy Cut-Off (ECO) tripped on certain A. O. Smith gas-control generations (same family of fault as 3-flash on those controls). Not present on the Honeywell-type map that uses 4/5/7/8. Confirm against the unit's gas-valve label pro repair	ECO tripped from over-temperature; temperature-control fault	confirm the temperature dial setting; confirm combustion-air openings are clear; turn the gas control OFF and arrange service
-, –, —	Voltex hybrid: unit is performing a normal system self-diagnostic at start-up. Not a fault DIY-checkable	normal power-up self-test	no action needed; wait for the display to finish the self-check
ICE	Voltex hybrid: the heat pump is in a normal defrost cycle. Not a fault DIY-checkable	normal defrost of the evaporator coil in cool/humid conditions	no action needed; the unit resumes automatically after defrost
HPO	Voltex hybrid: heat-pump-only status indication – ambient is in range (about 45-120 F) and average tank temperature is at/below its setpoint band, so the heat pump is the active heat source. Informational, not a fault DIY-checkable	normal heat-pump operating state	no action needed
SF	Voltex hybrid: the air filter is dirty and needs cleaning (service-filter reminder) DIY-checkable	accumulated dust/lint on the intake air filter	turn off power to the unit and clean or rinse the air filter per the owner manual, then restore power
ECF	Voltex hybrid: the heat-pump compressor is short-cycling (starting/stopping too frequently) pro repair	dirty air filter restricting airflow; loose/faulty fan connection; low or out-of-range ambient airflow	turn off power and clean the air filter; confirm the air space and any ducting around the unit are not blocked; if it persists, arrange service
EUC	Voltex hybrid: upper-element connect fault – the upper heating element is not functioning pro repair	failed upper heating element; loose/corroded element wiring connection	confirm the heater has power at the breaker (single reset of the breaker is acceptable); arrange service – element diagnosis/replacement requires a technician
ELC	Voltex hybrid: lower-element connect fault – the lower heating element is not functioning pro repair	failed lower heating element; loose/corroded element wiring connection	confirm the heater has power at the breaker; arrange service for element diagnosis/replacement
E20 / E21	Voltex hybrid: upper water-temperature sensor short (E20) or open (E21) – the upper temperature sensor is not functioning pro repair	failed upper temperature sensor; sensor wiring fault	no homeowner repair is possible; arrange a qualified technician
E30 / E31	Voltex hybrid: lower water-temperature sensor short (E30) or open (E31) – the lower temperature sensor is not functioning pro repair	failed lower temperature sensor; sensor wiring fault	no homeowner repair is possible; arrange a qualified technician
E10 / E11	Voltex hybrid: heat-pump coil (evaporator) temperature sensor short (E10) or open (E11) – the coil temperature sensor is not functioning pro repair	failed coil temperature sensor; sensor wiring fault	no homeowner repair is possible; arrange a qualified technician
E40 / E41	Voltex hybrid: heat-pump discharge temperature sensor short (E40) or open (E41) – the discharge temperature sensor is not functioning pro repair	failed discharge temperature sensor; sensor wiring fault	no homeowner repair is possible; arrange a qualified technician
E50 / E51	Voltex hybrid: heat-pump suction temperature sensor short (E50) or open (E51) – the suction temperature sensor is not functioning. (On some manuals labeled the ambient/suction sensor.) pro repair	failed suction temperature sensor; sensor wiring fault	no homeowner repair is possible; arrange a qualified technician
EDH	Voltex hybrid: heat-pump discharge temperature is too high (high-discharge lockout protecting the compressor) pro repair	refrigerant-circuit issue; airflow restriction; compressor/control fault	confirm the air filter is clean and airflow around the unit is unobstructed; if it persists, arrange a qualified technician
Edr	Voltex hybrid: dry-fire / low-water condition – not enough water in the tank to safely energize heating DIY-checkable	tank not fully filled after install or service; air trapped in the tank; cold-water supply not opened	confirm the cold-water supply valve to the heater is open; open a hot-water tap and run it until water flows continuously to confirm the tank is full and purge air; then restore power
EPL	Voltex hybrid: power-supply (line) voltage is too low for safe operation pro repair	low incoming line voltage; undersized/shared circuit; loose supply connection	confirm the unit is on its own properly rated circuit and the breaker is on (single reset is acceptable); if the code persists, have an electrician/technician verify supply voltage
ERROR 0-9 (e.g., ERROR 3)	Voltex hybrid: powered-anode fault – the powered anode rod is not operating properly (the trailing digit identifies the specific condition) pro repair	loose anode connection; failed powered-anode module; control fault	no homeowner repair is possible; arrange a qualified technician (A. O. Smith Residential Technical Assistance)

A. O. Smith water heater codes we get called for most

3 flashes (alternate control generations) — Over-temperature / Energy Cut-Off (ECO) tripped on certain A. O. Smith gas-control generations. On other (Honeywell-type) controls the same condition is shown as 4 flashes – always read the diagnostic label on the specific gas valve

Typical causes include eco tripped from over-temperature; blocked combustion air / thermal switch interaction; thermostat/gas-control fault. A few things are safe to check yourself (confirm the temperature dial is not set too high; confirm air intake around the heater base is unobstructed), but the repair is a licensed, TSBC-certified gas technician job. HeatLand diagnoses and fixes 3 flashes (alternate control generations) on A. O. Smith water heaters throughout Greater Vancouver.

Is it safe to keep running a A. O. Smith water heater with a fault code?

Most A. O. Smith fault codes put the water heater into a safe lockout for a reason. You can safely check the basics — the gas supply on, the pilot light or igniter, the temperature dial setting, the breaker on (power-vent/electric/hybrid models), and no water leaking around the tank — and restart it once. If the code returns, stop and book a technician. If you smell gas, leave the building and call your gas utility’s emergency line or 911 first. If a carbon-monoxide alarm sounds, get everyone out and call 911. Never cap or block the temperature & pressure (T&P) relief valve, and don’t keep relighting a pilot that won’t stay lit.

A. O. Smith water heater repair across Greater Vancouver

HeatLand has kept Metro Vancouver homes comfortable since 1999. Our licensed, insured technicians diagnose and repair A. O. Smith water heaters — pilot and ignition faults, gas-control (status-light) codes, sensor and thermostat errors, vent and air-intake blockages, leak shut-offs, and (on hybrid/heat-pump and tankless models) control-board and component faults — including units we didn’t install. We’re brand-agnostic, carry common parts, and give you an honest repair-or-replace assessment with upfront pricing and a free estimate. If your water heater is beyond economical repair, we’ll show you right-sized, high-efficiency replacement options and the rebates available.

Need it sorted fast? We offer priority emergency water heater repair. Explore Water Heater services, browse all water heater error codes by brand, or request a free estimate.

A. O. Smith water heater service areas

We repair A. O. Smith water heaters across Greater Vancouver and the Fraser Valley, including:

A. O. Smith water heater error code FAQs

Can I reset my A. O. Smith water heater myself?

Yes — power-cycling the reset button once is generally safe after you’ve checked the basics (the gas supply on, the pilot light or igniter, the temperature dial setting, the breaker on (power-vent/electric/hybrid models), and no water leaking around the tank). If the water heater faults again right away, stop and note the code — repeatedly resetting a water heater that keeps locking out can mask a real problem. Call a licensed, TSBC-certified gas technician to diagnose it.

What does the A. O. Smith 5 flashes code mean?

On A. O. Smith water heaters, 5 flashes commonly indicates temperature sensor failure: the control has detected a fault in the water-temperature sensor circuit. Confirm the exact meaning against your unit’s manual — codes can vary by model and series — and have the repair done by a licensed, TSBC-certified gas technician. HeatLand fixes this across Greater Vancouver.

Do you repair A. O. Smith water heaters you didn’t install?

Yes. HeatLand is brand-agnostic and services A. O. Smith water heaters throughout Metro Vancouver and the Fraser Valley, whether or not we installed the unit. We carry common parts and give you an honest repair-or-replace assessment.

Is a A. O. Smith water heater fault code an emergency?

No heat in cold weather is worth treating urgently. If you smell gas, leave the building and call your gas utility’s emergency line or 911 first. If a carbon-monoxide alarm sounds, get everyone out and call 911. Never cap or block the temperature & pressure (T&P) relief valve, and don’t keep relighting a pilot that won’t stay lit. For priority water heater repair across Greater Vancouver, call (604) 330-3812.

How much does A. O. Smith water heater repair cost in Vancouver?

It depends on the fault. Many A. O. Smith codes point to sensors, ignition or pump parts — usually far cheaper than replacement. We give upfront pricing and a free estimate before any work.

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