AO Smith Water Heater Troubleshooting Lights

AO Smith Water Heater Troubleshooting Lights [Complete Guide]

What I will break down on this in-depth guide on AO Smith Water Heater Troubleshooting Lights: 

  • What does flashing light mean on AO Smith Water Heater? 
  • 8 Common status light flashing codes
  • Break down what troubleshooting steps you should take to stop the blinking lights

Without further ado, let’s dive in. 

Table of Contents

What Does Flashing Light Mean On Ao Smith Water Heater?

It depends on how many times the flashing light is blinking. If your AO Smith Water Heater status light flashes 1 time every 3 seconds, it indicates your water heater runs at its best condition. 

On the other hand, your AO Smith Water Heater goes through problems if the status light flashes more than 1 times followed by a three-second pause. 

For example, if the status light blinks 2 times, there is an issue with the thermopile voltage output. In contrast, 4 consecutive flashes with a 3-second pause indicates the temperature sensor of the unit senses the water temperature is too high. 

Below, I will explain the meaning of status light codes and what steps you should take to stop the blinking light. 

AO Smith Water Heater Troubleshooting Lights [8 Common Blinking Light Codes]

This chapter will discuss everything you need to know about the flashing light codes on AO Smith Water Heater. 

01. Status Light Flashing 0 Times

The LED status light flashes 0 times or it doesn’t come on due to two reasons. First, the pilot light won’t come on until you try to light it up. Second, the thermopile of your gas water heater has not reached its operating temperature yet. 

How To Fix: 

Whether you have a newly installed AO Smith Gas water heater or an older one, you must light up the pilot first. Otherwise, the status light won’t blink. Go along with the following steps to light up your water heater: 

  • Turn the gas control knob to the off position by moving it counter-clockwise. 
  • Wait for ten minutes to allow all the gas to clear out.
  • Now, set the gas control knob to the Pilot position. 
  • Press down the gas control knob all the way in while depressing the igniter button continuously. You should keep depressing the igniter button for 90 seconds. 
  • Release the gas control knob once the status light starts flashing and set the temperature to your desired setting. 

Secondly, the status light won’t flash a single time until the thermopile reaches its normal operating temperature. Generally, it takes up to 90 seconds of continuous pilot operation before the thermopile reaches its operating temp. 

If the status light still doesn’t come on, I bet the pilot flame fails to heat the thermopile sufficiently. In other words, the thermopile itself gets defective or the wire connectors come loose. 

Regarding this, you need to replace the thermocouple or the wire connectors. 

02. Status Light Remain Solid Red

Does the status light of your AO Smith Water Heater remain solid red? If yes, it’s because the pilot light got extinguished recently and the thermopile is cooling down. 

How To Fix: 

Turn the gas control valve to the off position in the first place. Now, wait for 10 minutes to let the thermopile cool down. Then, relight the pilot by following the lighting instructions I mentioned in the previous chapter. 

It may take 90 seconds of pilot operation before the thermopile comes to its normal operating temp. Once the thermopile reaches its operating temperature, the status light will no longer remain solid red. 

You May Find Interesting: Rheem Gladiator Solid Red Light

03. Status Light Flashing 1 Times

The status light flashes 1 times with a three-second pause indicating your water heater operates at its tip-top condition. It means you don’t need to worry about anything. 

How To Fix: 

You don’t need to take any corrective actions as the status light of a functioning unit blinks 1 time every 3 seconds. 

04. Status Light Flashing 2 Times

Two consecutive flashes every three second stand for thermopile voltage issue. In this case, the pilot light will be lit but the thermopile fails to generate the required output voltage. 

How To Fix: 

Start with turning off the gas control valve to the off position. The thermopile of your water heater can’t produce the required voltage output for two reasons. Firstly, the thermopile is at fault. And secondly, loose wiring connections can also cause this symptom. 

So, the corrective action you need to take is- check the thermopile and replace it if it gets defective. And this tutorial will help in replacing the thermocouple on the AO Smith Water Heater: 

Secondly, inspect the wire connectors for loose. If they come loose, tighten them up. 

05. Status Light Flashing 4 Times

When the temperature sensor senses the water temperature is excessively hot, the status light will flash 4 times. Once this problem occurs, the main burner will go into the off position along the pilot light immediately. You can see the flash code once you relight the pilot light. 

How To Fix: 

First off, relight the pilot following the steps I mentioned earlier to verify the status light is blinking 4 times. Once you confirm the issue, turn off the gas control knob. Then, shut off the main gas supply valve. 

Generally, the water gets too hot if the gas control valve/thermostat is at fault. To fix this issue, you should replace this part. 

Replacing the gas control valve/thermostat will be a simple fix to this issue. Follow the below steps to change the part correctly: 

  • Ensure you turn the gas control knob to the off position.
  • Turn the gas supply off at the manual shut-off valve on the gas supply line. 
  • Drain your water heater. Just connect a garden hose to the drain plug at the bottom of the unit and place the other end of the hose to the nearest floor drain. Now, turn on the drain valve to let the water drain. 
  • Disconnect every connection like the igniter wire, thermopile wire, pilot tube, and manifold tube from the gas control valve. 
  • Now, remove the ground joint union in the gas piping and disconnect the remaining piping from the gas control valve. 
  • Next, thread a 4” section of gas pipe into the inlet and use it to turn the gas control valve counter-clockwise to remove the gas control valve. 
  • Install a new gas control valve and tighten it up using the 4” gas pipe by turning it clockwise. 
  • Don’t forget to use Teflon tape on the gas piping connections and fitting on the back of the gas valve that screws into the tank. 
  • Once you install the gas control valve, put every connection like the igniter wiring, pilot tube, and others back into the valve. 
  • Turn the gas supply on and check for leaks by spraying soap solution on the connections. 
  • Fill the water tank with water.
  • Finally, light the pilot light. 

06. Status Light Blinking 5 Times

Your AO Smith Water Heater’s status light will blink 5 times every three seconds if the temperature sensor gets defective. To bring your water heater to a normal operating state, you should replace the temperature sensor. 

How To Fix: 

First off, turn the gas control knob to the off position. Then, watch this tutorial and follow the steps to get the temperature sensor replaced:

07. Status Light Flashing 7 Times

If you observe the status light of your water heater flashes 7 times consecutively with a three-second pause, understand the gas valve is at fault. To solve this issue, there is no way except replacing the gas control valve. 

How To Fix: 

Changing the gas control valve is not as difficult as you assume. Just follow the step-by-step instructions I mentioned in the ‘Status Light Flashing 4 Times’ section. Alternatively, you can watch this video that will come in handy: 

08. Status Light Flashing 8 Times

AO Smith Water Heater Status Light will flash 8 times every 3 seconds if the gas control valve is in the off position but the thermopile still produces electric power. This problem occurs because of two reasons. Either the thermopile doesn’t cool down quickly or the pilot valve is stuck in an open position. 

How To Fix: 

What should you do first is- turn the gas control valve to the off position. Then, leave the unit for 10 minutes to let the thermopile cool down. Now, relight the pilot light by following the step-by-step guide I mentioned earlier in this article.  

Secondly, you must replace the gas control valve if the pilot valve gets stuck in an open position. Regarding this, follow the instructions I broke down in the ‘Status light flashing 4 times’. 


Why is my AO Smith water heater not lighting?

Your AO Smith Water Heater won’t light up if there are electrical problems like the thermopile wires come loose.

Should the water heater light be blinking?

Yes, the heater heater light should blink as the flashing light will help you to understand whether the heater is working properly or not.

How long does an A.O. Smith water heater last?

AO Smith water heaters are designed to last. If you install the unit professionally and maintain it according to the manual, it will support you for up to 10 years.


A flashing status light doesn’t seem scary all the time. You can easily detect the exact problem of your water heater if you know the meaning of the flashing light code. And this guide on AO Smith Water Heater Troubleshooting Lights broke down everything you need to know. As a result, you can now easily diagnose your water heater that will save you both time and money. So, it’s worth bookmarking this article.

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  1. Smith NG water heater Commercial Shut down. I turned off for 5 minutes then back on. Blue light now heartbeat dim & bright.

    1. Hey Jerry,

      It’s normal. Don’t need to worry about it. However, if it interrupts normal water heater operation, don’t hesitate to call a plumber. Thank you.

  2. Hi, On an Electric AO SMITH Smart Water Heater, if the diag light is a solid red (looks more orange) right after you flip breaker on and the smart panel has no lights/codes. What could that be?

  3. Status light blinking once every 3 seconds but I don’t see a flame in the window

    1. Hey Amber,

      I recommend you turn the unit off and relight the pilot. If this doesn’t bring any luck to you, the best bait is to call a professional for further assistance.

      Good Luck…

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