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AO Smith Tankless Water Heater Troubleshooting

What happens if you try to use the hot water faucet and it only gives you cold water? There’s always the possibility that your water heater could stop working when you need it to take a hot shower. The fact that you can’t go online right away is, well, irritating!

A weird water heater code flashing in your face doesn’t help. AO Smith tankless fault codes might be confusing, but we’re here to help you decipher them.

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However, this will necessitate people to learn more about inexpediently AO Smith Tankless Water Heater Troubleshooting to understand the error and the solution. With that being said, here in this article, we’ve listed a few error codes and discussed their solution.

Is There A Way To Find AO Smith Water Heater Errors?

Is There A Way To Find AO Smith Water Heater Errors

Tankless water heaters from AO Smith that are fitted with a remote controller have a significant benefit; they offer a self-diagnosing capability that assists in diagnosing heating problems. 

If there is a problem with the water heater, a sound will be made by the installed remote, and an error number will be shown on the screen.

These codes can be displayed on remote controls for some models, like the 240, 340, and 540 series. Similarly, an error code will also be displayed on the appliance’s LED display in place of the temperature.

However, in a model like the 510 series, a message indicating an error code will be displayed on an LCD. Others, like the 110 and 310, have a red light on the appliance that blinks rapidly. 

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When an error occurs, the light blinks a different number of times. But it’s better to check your owner’s manual to determine what model you have and where the error code can be found.

AO Smith Tankless Water Heater Troubleshooting

Here’re the error codes you’ll see if your water heater was installed correctly in accordance with the manufacturer’s specifications.

Error Code 031, Flash One Time

What Is It?

If you’re having error code 31, that means some problem arises in the setting of the water heater’s dipswitch.

Troubleshooting

First of all, stop the power supply. After removing the front cover, you’ll find the dipswitches. Now it’s time to check the dipswitches and make sure they have been installed correctly.

Error Code 101, Flash Five Times

What Is It?

This is an alarm code that indicates abnormal combustion.

Troubleshooting

First, check if there’s any blockage in the airflow. To do so, you can check the fan, venting length obstruction, heat exchanger, etc.  And if necessary, make adjustments to the manifold pressure to achieve the desired results.

Lastly, clean the fan motor and gas burner if they’re dirty or greasy. Ensure that the inlet is free of debris, such as dust and grease. Finally, restart the system after all the installation.

Error Code 111, Flash Three Times

What Is It?

An ignition failure means that the unit will not turn on after three failed attempts to start it.

Troubleshooting

Verify that the hi-limit switch is functioning properly and that no wires or connections are loose. Make sure to call for help if it’s tripping and you don’t know why it’s doing so.

Then check the flame rod if there’s any coal dust or not. Lastly, examine the computer board to ensure that it isn’t damaged and no loose wires or connections.

Error Code 121, Flash Three Times

What Is It?

During operating, there’s a reduction in the amount of flame.

Troubleshooting

First, check the hi-limit switch and computer board. Then check to see that there’s no obstruction in the gas supply and the gas is turned on at the proper pressure. However, vents may be obstructed, so look for them.

Error Code 311, Flash Two Times

What Is It?

This is an output thermistor (heater’s component that produces a modest electric current) error.

Troubleshooting

Inspect wire connections to ensure that they’re secure and free of burns or cuts. The output thermistor is located on the right side of the heat exchanger, near the bottom. Check the resistance value; it should be around 74°F at room temperature.

Error Code 321, Flash Two Times

What Is It?

This error is shown when a failure is found on the outlet thermistor.

Troubleshooting

There should be no damage to the thermistor wiring connection. That’s why clean the thermistor if it has become clogged with dirt or debris, if necessary. Still, if the code error continues to occur, the outlet thermistor should be replaced.

Error Code 331, Flash Two Times

What Is It?

An error occurred in mixing the thermistor.

Troubleshooting

The thermistor wiring connection should be undamaged. That’s why it’s important to clean the thermistor if it gets clogged with dirt or debris. Even so, if the code error persists, it’s time to get a new outlet thermistor.

Error Code 341, Flash Two Times

What Is It?

This is the alert of the failure of the exhaust thermistor.

Troubleshooting

Check the thermistor and clean it thoroughly.

Error Code 391, Flash Two Times

What Is It?

This is the air-fuel ratio (AFR) failure.

Troubleshooting

To be safe, make sure the wire connections are tight and no cuts or burns on them. Check if the clear plastic tube that connects the proportional gas valve to the combustion chamber has been properly installed. Lastly, clean up the AFR if needed.

Error Code 441, Flash Two Times

What Is It?

This code means that the flow sensor isn’t working properly. As a result of the master unit signalling another heater to begin operation, the latter fails.

Troubleshooting

Find out if there’s a water supply to the heater that’s out of order. To prevent damage to the computer board, check for frayed or broken wires. The inlet filter should be free of debris. Lastly, make sure the flow sensor is clean.

Error Code 510, Flash Six Times

What Is It?

A problem arises in gas valves.

Troubleshooting

Shut off gas and power to the unit immediately if the hot water is turned off, but flames are still visible through its sight glass. Inspect all the wires connecting the gas valve assembly for burns or cuts.

Ensure that each gas valve wire is connected to the correct location if the device has recently been repaired. After all, these make sure the supply gas pressure is within the specified range.

Error Code 611, Flash Four Times

What Is It?

The code indicates the abnormality found in the fan motor.

Troubleshooting

Examine the fan motor wiring for damage and the PC board for moisture. Before turning the power back on, if there’s any moisture, allow it to dry thoroughly. If the problem still persists, a new computer board may be required.

Error Code 651, Flash Four Times

What Is It?

There’s a problem with the flow control valve.

Troubleshooting

Turn off the electricity first. Wire connections must be safe and free of burns. The cold water inlet is connected to the flow adjustment valve, hidden behind the computer board. Check the valve for water leakage and clean the flow adjustment valve if any dirt or debris is found.

Error Code 661, Flash Four Times

What Is It?

Damage found in bypass valve.

Troubleshooting

First, you have to check the flow adjustment valve for any damage. And then check if there’s any build-up on the motor drive. However, don’t forget to check for any water leakage.

Error Code 701, Flash One Time

What Is It?

The motherboard of the computer is malfunctioning.

Troubleshooting

You should ensure that all of the cables are connected correctly and that there’re no fractures in them. Take a good look at the board for any signs of a burn or cut. Check to verify that the machine has a working power supply.

Error Code 711, Flash One Time

What Is It?

The gas solenoid valve driving circuit has failed.

Troubleshooting

Wire damage should be looked for in the hi-limit and overheat cut-off switches. Don’t forget to check the gas valve’s control board connection.

Error Code 721, Flash One Time

What Is It?

The error shows the false flame detection.

Troubleshooting

All gas and electricity must be cut off first. The flame sensor may be the source of the issue. To get further help, contact the Technical Service Department.

Error Code 741 and 751

What Is It?

The water heater and the remote controller aren’t communicating properly. You may experience these errors if you unplug the heater’s remote from the power source while the heater is running.

Troubleshooting

Before unplugging the remote, turn the power off. You should verify that the remote and the water heater are properly connected. Get the right remote control before starting.

Signs of damage, such as burned wires or a faulty control board, should be looked for. LCD screens may flash if the power is off for a brief period.

Error Code 761

What Is It?

In an Easy-Link system, there is a communication breakdown between master and slave units. This error message indicates that the master unit has lost contact with the heater it is referring to. 

Troubleshooting

Verify that the item that has lost communication is receiving electricity. If you’re not sure how to set up communication cables, go to the Installation Manual. Do a visual inspection for indicators of voltage spikes.

Error Code 991, Flash Five Times

What Is It?

Inadequate gas combustion is what the code is showing.

Troubleshooting

If you’ve tried everything else and nothing has worked, contact the Technical Service Department. The gas pressure in the manifold may need to be adjusted. Restart the computer if you’re certain that the issue has been resolved.

FAQs on water heater troubleshooting

  • Why does a tankless water heater beep?

If there’s a problem with your tankless water heater, it’ll “beep” and show an error code. In the event of a breakdown, malfunction, or leak, tankless water heaters will emit an audible alarm.

  • Should I switch off my tankless water heater if the water is off?

As tankless and point-of-use water heaters don’t operate heating elements constantly or store water in a tank, they don’t need a water shutdown.

  • How can I alter the AO Smith tankless water heater’s temperature?

Both thermostats should be set at 120 degrees Fahrenheit. Turn the water temperature dial clockwise (>>) to raise the temperature if necessary. To lower the temperature, turn the dial counterclockwise ().) Both thermostats should be set to the same temperature.

  • How often should tankless water heaters be flushed?

Every year, tankless water heaters must be cleansed to ensure proper operation. Residents with hard water should flush and clean their water treatment systems more often, potentially every six to nine months.

Final Thoughts on AO Smith Water Heater Troubleshooting

Now that you’ve learned a bit more about AO Smith Tankless Water Heater Troubleshooting, you’ll be able to start repairing any issues on your own. 

Just keep in mind that if you’re unsure about anything, you should contact a service specialist. When it comes to gas and electricity, safety is of the utmost importance.

Related Resource:

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