Start with the power cord. A gas tank with no cord and a knob-style Honeywell gas valve has a single status light, and that light is the whole diagnostic system. A gas tank with a cord and a blower on top is a power-vent model.
Many power-vent tanks carry the White-Rodgers Intelli-Vent control: six LEDs across the face, one green and five yellow on residential versions, all of them dark in normal operation. A. O. Smith calls that sleep mode, so on this control any lit LED is a fault. Other power-vent models, the GPVL series among them, use a Honeywell electronic control that flashes instead: two flashes for a pressure switch failed closed, three for failed open.
On the Honeywell status-light valve, the pilot heats a thermopile and the thermopile powers the electronics. It needs at least 350 millivolts under load to hold the valve open and run the light. Two things follow that catch people out: the light can take up to 90 seconds of steady pilot before it starts blinking, and the control requires a 10-minute wait between lighting attempts. Bradford White tanks use a similar status-light approach with their own legend: see the Bradford White water heater error code guide.
A. O. Smith tankless heaters are built on Takagi's platform and show three-digit codes such as 111 and 121. Those are in the Takagi tankless error code guide, not here. Codes vary by model, series and year, and the label on your own tank is the authority: where it disagrees with this page, the label wins. The A. O. Smith water heater repair page has more on the models we service, and ZK Mechanical is happy to sort out which control you have from a photo.
A. O. Smith water heater codes, decoded
| Code | What it means | Safe? | Try first | When to call |
|---|---|---|---|---|
No light (0 flashes) | Honeywell status-light valve: control off or pilot out. Also normal for the first 90 seconds after lighting, until the thermopile warms up. | turn it off | Follow the lighting instructions on the tank, then confirm the pilot through the viewport. | If the pilot lights but will not hold, or will not light at all. |
Solid light | Pilot was recently extinguished and the thermopile is still cooling down. | turn it off | Turn the knob to OFF, wait 10 minutes, then relight. | If it goes out again the same day. |
1 flash | Normal operation: a bright and dim heartbeat about every three seconds. | keep running | No action. | No call needed for the light itself. |
2 flashes | Thermopile voltage low. | keep running | Check for condensation dripping on the burner area after a heavy draw on a cold tank. | Soon. Below 350 millivolts the thermopile is replaced. |
4 flashes | Temperature exceeded: the ECO (energy cut-off) has activated. | turn it off | Knob to OFF and close the gas supply to the heater. | Yes. A. O. Smith's instruction is to replace the gas control valve. |
5 flashes | Sensor failure inside the gas control valve and thermostat. | turn it off | Set the knob to OFF and shut the gas to the tank. | Yes. The remedy in the handbook is a new control. |
7 flashes | Internal control failure. | turn it off | Turn the control off at the knob and the gas off at the pipe. | Yes. This is a replacement, not a reset. |
8 flashes | Power off failure. If the pilot is still burning with the knob at OFF, the valve has not closed. | call now | Look through the viewport. Flame with the knob at OFF means close the gas shutoff on the supply pipe. | Immediately if the pilot is burning with the control off. |
Intelli-Vent 1 or 2 | Electrical supply faults: 1 is no earth ground sensed, 2 is reversed polarity at the outlet or in the wiring. | turn it off | Plug the heater straight into its wall outlet, not an extension cord or power bar. | An electrician if the outlet is at fault; us if the heater's wiring is. |
Intelli-Vent 3 | Pressure switch circuit stays closed for more than five seconds after a heating cycle starts. The blower does not start. | turn it off | None. | Yes. The switch is tested for a stuck contact. |
Intelli-Vent 4 | Pressure switch circuit stays open after the blower is energized. The blower may run continuously. | turn it off | Check the vent termination and intake outside for snow, ice, leaves or a nest. | If the vent is clear. Sensing tube, vent length, blower and the vent temperature switch are next. |
Intelli-Vent 5 | Ignitor failure: the control has detected an open hot-surface ignitor circuit. | turn it off | None. | Book a repair. The ignitor assembly and its plug are checked. |
Intelli-Vent 6 | Ignition or flame failure. The heater has used up its retries and locked itself out for one hour. | turn it off | Confirm the gas is on. Cycle the power off and on once to reset. | If it locks out a second time. |
Intelli-Vent 7, 8, 9 | Internal control failures: the gas valve driver circuit, the microprocessor or internal circuits. | turn it off | Power off for 10 to 20 seconds, then back on. | If the code cannot be cleared, the control is replaced. |
Intelli-Vent 10 | Flame sensed out of sequence. | call now | Unplug the heater and close its gas shutoff valve. | Immediately. |
Intelli-Vent 11 | High temperature cutoff (ECO) activated: tank water went past about 90°C. | turn it off | One power-off of 10 to 20 seconds is allowed to try to clear it. | If it does not clear. On residential controls the ECO is single-use and the control is replaced. |
Intelli-Vent 13 | Temperature probe (thermistor) open or shorted. | turn it off | None beyond one power cycle. | Book a repair. |
Intelli-Vent 14 or 15 | The resistor wire on the ignitor assembly plug is open, shorted or out of tolerance. | turn it off | None. | Book a repair. The wire must never be cut or bypassed. |
Hybrid 001 | Hybrid heat pump models: dry-fire protection. Power is on and the tank is not completely full of water. | turn it off | Breaker off. Open a hot tap until water flows with no air bursts, then restore power. | If the tank is full and 001 remains. |
Hybrid 080 | Hybrid heat pump models: the air filter is dirty. | keep running | Breaker off, lift the filter out of the top of the unit, vacuum it and put it back. | Only if the alert stays after cleaning. |
The codes that usually mean a real repair
2 flashes: the thermopile
The thermopile sits in the pilot flame and makes roughly 750 to 900 millivolts with nothing connected. Once it sags below 350 under load, the valve can no longer hold open and the light reports it. Before condemning it we check the wiring connections and rule out condensation dripping onto the burner. A thermopile or pilot assembly is one of the smaller repairs on a gas tank, typically in the $150–$300 band.
4, 5 or 7 flashes: the gas control valve
For all three of these the A. O. Smith service handbook gives the same remedy: knob off, gas off, replace the gas control valve and thermostat. Gas control replacement is $400–$600. What matters after a four-flash code is why the tank overheated, so we look at the temperature setting and how the heater is being used, not only the part. On an older tank it is fair to price a replacement tank beside the repair.
Intelli-Vent 4 or 6: vent, pressure switch and ignition
Code 4 is nearly always about air: a blocked termination, too many elbows, a kinked sensing tube, lint on the blower wheel, or a vent temperature limit switch that opened because flue gas ran hot. Code 6 follows three failed trials for ignition or three flame losses, and gas supply, a dirty flame sensor and ignitor position are the checks. A homeowner can safely look at the vent termination, the power and the intake, and nothing else. Why a power-vent water heater runs but will not ignite covers the sequence.
Licensed technicians, a written price before the repair, no overtime charges.
Common questions
My power-vent A. O. Smith has no lights on at all. Is the control dead?
Probably not. An Intelli-Vent control keeps every LED dark during normal operation for the life of the heater. To see the temperature setting, hold both temperature buttons together for about a second and the LEDs wake up, then go dark again after 30 seconds. If there is no hot water and the LEDs will not wake, check the plug, the outlet and the breaker.
I relit the pilot and the status light is not blinking. Did it fail?
Give it time. The Honeywell valve's light is powered by the thermopile, and A. O. Smith's handbook says it can take up to 90 seconds of continuous pilot before the light starts. If you let go early and the pilot dropped out, the control also makes you wait 10 minutes before the next attempt. A pilot that holds with no light after that needs testing.
Can I clear an Intelli-Vent code 6 lockout myself?
Once. The control locks out for an hour after it runs out of ignition retries, and cycling the power off and on resets it. If the burner lights and stays lit, a brief gas interruption may have been the cause. If it locks out again, stop: the control has now failed to light or hold flame six times, and that calls for a technician with a manometer.
What codes does an A. O. Smith hybrid heat pump water heater show?
Three-digit numbers with a flashing alert icon. The ones a homeowner can act on are 001 for dry-fire protection, 080 for a dirty air filter and 081 for condensate management, which means a blocked drain line or a condensate pump that is not running. Compressor codes in the 083 to 085 range are refrigeration faults and are not a do-it-yourself repair.
Who fixes an A. O. Smith tank that is a rental?
The rental company. Many water heaters in Ontario homes are rented, and the sticker on the tank names the provider whose job it is to repair or replace it. If the tank is your own, the usual numbers apply: a $90–$150 diagnostic credited to the repair, and most repairs between $150 and $800. Book through our water heater service page.