The short answer
On an A. O. Smith gas water heater in Northern Virginia, count the flashes on the gas control’s status light. One slow blink every few seconds is normal. Two flashes means a weak pilot signal, four means the water overheated, five means the temperature sensor failed, seven means the gas control failed, and eight means it sees a flame with the knob off. Four, seven and eight all end with the gas control replaced. State and Reliance tanks are A. O. Smith brands and usually use the same controls.
The gas control chart
Watch the light for a full minute. Count the quick flashes between pauses, then count a second round to be sure.
Swipe to see all columns →
Swipe to see all columns →
| The light | What it means | What to try first |
|---|---|---|
| One blink every 3 seconds | Normal | Nothing |
| No light | The pilot is out, or the knob is off | Relight it by the label. Our steps walk through it |
| Steady on, not blinking | The pilot just went out and the control is cooling down | Wait 10 minutes, then relight |
| 2 flashes | Weak pilot signal: the thermopile, or a dirty pilot | Look for lint on the air screen at the base, then call |
| 4 flashes | The water overheated and the safety opened | Turn it off and call. A. O. Smith’s manual says the control gets replaced |
| 5 flashes | The temperature sensor failed | Call |
| 7 flashes | The gas control failed | Call. The control gets replaced |
| 8 flashes | Flame seen with the knob off: the valve may be stuck open | Shut the gas valve on the line to the tank and call |
$99 Water Heater Flush
We drain and flush the tank, check the anode rod and test the relief valve, then go through the house's plumbing with photos, included. See the flush
Want your own number before anyone comes out? The water heater estimator prices your house in a few questions.
Power vent models
A. O. Smith power vent tanks have a blower on top and a plastic pipe to the outside, and most of their codes are about proving the vent is clear before the burner lights:
Swipe to see all columns →
Swipe to see all columns →
| Flashes | What it means | What to check |
|---|---|---|
| 2 | The pressure switch is closed before the fan starts | Call: a stuck switch |
| 3 | The pressure switch or the blower’s thermal switch is open | The vent outside: leaves, a nest, snow. Then the little hose to the switch |
| 4 | The thermal cutoff tripped | Turn it off and call |
| 6, then 1 | It tried to light and couldn’t | Is the gas valve on the line open? Then call |
| 6, then 3 | It lit and the flame went out | Call: usually the flame sensor or the gas supply |
| 7 | The flammable vapor sensor tripped | Move anything flammable away from the tank and call |
Power vents need power. A tripped GFCI outlet or a breaker that’s off looks like a dead water heater, so check those before anything else. Here’s what a power vent tank looks like.
Electric A. O. Smith tanks
Standard electric models have no flash codes. They have a red reset button behind the upper panel, and our reset button post shows how to press it safely and what it means when it keeps tripping.
How old is my A. O. Smith?
Since 2008, the first four digits of the serial number are the year and the week it was made. A serial that starts 1532 was built in the 32nd week of 2015. That’s the number to know before you put money into a gas control. More on reading the age of any water heater.
A drip is usually pressure, not the tank
A relief valve that drips on an A. O. Smith, or any tank, is almost always thermal expansion or high house pressure. Here’s why a relief valve drips and how to test it, and if the drip is coming from the bottom of the tank instead, that one is different.
Repair or replace
A thermopile or a pilot cleaning is a normal repair. A gas control on a tank that’s 10 or more years old is where we’d stop and weigh a new tank; here’s how long a water heater lasts. We repair and replace A. O. Smith tanks across Northern Virginia; more on our A. O. Smith page. Have a Bradford White too? Its codes are here.
On a tank with years left, the water heater flush is $99 (normally $199): we drain and flush the tank, check the anode rod and test the relief valve. On an old one, the water heater estimator shows your installed price first, and $500 comes off it.
Book it
A plumbing diagnosis visit is $49, or $250 after hours, and you get the price of the fix before we start. Call (703) 997-9757, day or night, or book the water heater flush from goswiftpro.com/cookiesoffer by November 30 and a box of warm MOLTN cookies comes with it. Every current deal is on our offers page. Rated 5.0 stars across 1,138 reviews on Google, Angi, Yelp, the BBB and Facebook, Virginia Class A license 2705192276.
Questions people ask
Why is my A. O. Smith water heater blinking?
A slow blink every 3 seconds is normal. A count of quick flashes with a pause is a code: 2 is a weak pilot signal, 4 is an overheat, 5 is a bad temperature sensor, 7 is a failed control.
What does 7 flashes mean on an A. O. Smith water heater?
The gas control has failed, and it gets replaced. On an older tank, compare that repair to a new tank first.
How do I reset an A. O. Smith water heater?
Gas models have no reset; turn the knob to OFF, wait, and relight by the label. Electric models have a red reset button behind the upper panel, with the breaker off.
How do I read the date on an A. O. Smith serial number?
Since 2008, the first four digits are the year and the week. 1532 means the 32nd week of 2015.
Are State and Reliance the same as A. O. Smith?
Both are A. O. Smith brands, and their gas tanks usually use the same controls and codes.
