A. O. Smith Blinking Green Light: Normal or a Fault?
On this page (6 sections)
The Short Answer: On most A. O. Smith standing-pilot gas heaters, a single flash that repeats every few seconds, often described as a bright-dim “heartbeat”, means the control is working normally. A count of two or more flashes followed by a three-second pause is a fault code. A. O. Smith lists 2 flashes as low thermopile voltage, 4 as an overheat shutdown, and 5, 7 and 8 as control faults.
Is your blink normal?
The status light sits on the front of the gas control, near the temperature knob. A. O. Smith’s documents describe it by flash pattern rather than colour, so whether yours looks green or white does not change the meaning.
Watch it for at least two full cycles:
- One flash, repeating, and the water is hot: normal. No action needed.
- One flash, repeating, but the water is cold: the control is fine. Check the temperature knob is not on a low or vacation setting, then look for a heating problem such as burner on but no hot water.
- Several flashes, then a pause of about three seconds, repeating: a fault code. Count the flashes and use the table below.
- No light at all, or a steady light: see A. O. Smith blinking white light, which covers lighting and the patterns that are not fault codes.
A. O. Smith flash codes on standing-pilot FVIR models
These meanings come from A. O. Smith’s service handbook for residential FVIR gas water heaters (opens in a new tab) (the GCV, GCVH, GVR, GCVL, GVRL and GCVT series and their XCV-family counterparts). Models with an electric flue damper, a power vent, or electronic ignition use different tables.
| Flashes, then a 3-second pause | What A. O. Smith says it means | What usually follows |
|---|---|---|
| 1 (heartbeat) | Normal operation | Nothing |
| 2 | Thermopile voltage low | Technician checks wiring and thermopile output; thermopile may be replaced |
| 4 | Temperature exceeded; the energy cutoff (ECO) has activated | Gas control replaced |
| 5 | Sensor failure | Gas control replaced |
| 7 | Internal control failure | Gas control replaced |
| 8 | Power off failure | If the pilot stays lit with the knob off, gas control replaced; otherwise relight after 10 minutes and monitor |
Note what is missing: there are no 3-flash or 6-flash codes on this control. If you counted three, count again; if your heater really shows three, it probably has a different control, covered in A. O. Smith water heater blinks 3 times.
What the codes mean for you
Two flashes is the most common fault and the least serious. The thermopile is the part the pilot flame heats to power the control. If its output drops, the control may shut the burner down or fail to keep the pilot lit. Causes include a loose connection, a weak pilot flame, or a worn thermopile. A. O. Smith’s service handbook gives 350 millivolts as the point below which the thermopile is replaced; that measurement is a technician’s job.
Four flashes means the water got hotter than the control allows and the safety shut it down. A. O. Smith’s direction is to turn the control off, turn off the gas supply, and replace the gas control. Do not keep relighting it.
Five, seven and eight flashes are failures inside the gas control or its sensor. All point to a new gas control. Eight flashes with a pilot still burning after the knob is turned to OFF is a gas control that is not shutting off properly; turn off the gas supply valve to the heater and call for service.
What you can do
- Follow the lighting instructions on the heater’s label if the pilot is out. A. O. Smith’s control requires a 10-minute wait between lighting attempts, and the light may take up to 90 seconds of pilot operation before it starts blinking.
- Make sure the area around the heater is free of flammable liquids and that the air openings at the base are not blocked by stored items or lint.
- Write down the flash count and the model number from the rating plate before calling.
What the technician will check
For 2 flashes, the technician checks the thermopile wiring and measures its output, inspects the pilot flame, and cleans or replaces the pilot assembly or thermopile. For 4, 5, 7 or 8 flashes, they confirm the code and replace the gas control. On a heater that is near the end of its life, a gas control replacement is often the point to consider how old the heater is before paying for the part.
Frequently Asked Questions
Q: Is it normal for the light to blink all the time? A: Yes. On these controls the single repeating blink is a heartbeat showing that the pilot is lit and the control is powered. It is the counted patterns with a pause that indicate faults.
Q: Can I replace the gas control myself after a 4-flash code? A: No. Replacing a gas control involves disconnecting and reconnecting gas piping and testing for leaks, which is work for a licensed gas technician.
Manuals and supporting references
These links distinguish general safety information from model-specific documentation. A manual directory helps you locate your unit’s instructions; it does not establish that every model uses the same parts, codes, or test values.
- A. O. Smith service handbook 327726: residential FVIR gas water heaters (opens in a new tab)A. O. Smith GCV, GCVH, GVR, GCVL, GVRL, GCVT and XCV/XVR/XCVL/XGV/XVRL/XCVT series 300/301 residential gas water heaters.
- A. O. Smith: model and manual lookup (opens in a new tab)Find the instructions for the model on your rating plate; this directory does not verify a particular error-code meaning.
- PG&E: recognizing and responding to a gas leak (opens in a new tab)Emergency actions for suspected fuel-gas leaks.
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