AO Smith Hybrid Water Heater Troubleshooting [Complete Guide] (2023)

This is a complete troubleshooting guide for AO Smith Hybrid water heaters. In this article I will break down:

  • 7 Common Problems With Hybrid Water Heaters
  • Pinpoint the meaning of each AO Smith Hybrid Water Heater error code
  • How do you reset your AO Smith Hybrid Water Heater?

Without further ado, let's dive in.

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  • 1 AO Smith Hybrid Water Heater Troubleshooting [7 Common Problems]
    • 1.1 01. No hot water
    • 1.3 03. Smell of water
    • 1.4 04. Water heater sounds
    • 1.5 05. Temperature too high
    • 1.6 06. Low water pressure
    • 1.7 07. Insufficient hot water
  • 2 AO Smith Hybrid Water Heater Error Codes
    • 2.1 Error code "ICE" or "HPO"
    • 2.2 Error code "EUC"
    • 2.3 Error code "ELC"
    • 2.4 Error code "SF"
    • 2.5 Error code "ECF"
    • 2.6 Error code "E20-E60"
    • 2.7 Error code "Edr"
    • 2.8 Error code "EPL"
    • 2.9 Error code "EDH"
    • 2.10 Error code "EoF"
    • 2.11 ECL error code
    • 2.12 ECC error code
  • 3 How do I reset the AO Smith Hybrid Water Heater?
  • 4 Endnote

AO Smith Hybrid Water Heater Troubleshooting [7 Common Problems]

This chapter will guide you through the most common problems of a hybrid or electric water heater and their solutions.

01. No hot water

Some common reasons for an electric or hybrid water heater not providing hot water are:

  • Device has no power
  • Water heater is in vacation mode
  • The Eco or Reset button is triggered
  • The hot water consumption pattern may exceed the unit's capacity in the current mode
  • Upper heating element defective
  • Leak in the plumbing system.

How to fix:

Start by checking whether the water heater is getting power or not. No lights on your AO Smith Hybrid Water Heater means the unit is not receiving power. It occurs when there is a problem with your home's electrical wiring or circuit breakers.

I highly recommend you get a non-contact circuit tester to test the electrical wiring. First, locate the water heater circuit breaker and turn it to the off position. Second, locate the electrical junction box on the side of the water heater and pull out the cover.

Third, identify the two power wires - the power wires and the ground wires. Black/black or black/red are the colors of the power cables. On the other side, the copper or green is the ground wire.

(Video) Hybrid Water Heater Maintenance for all Brands - Rheem, AO Smith

Fourth, turn on the circuit breaker and check the two power wires with the non-contact circuit tester. If you are not getting power to your water heater, turn the breaker back off. Then reattach the connection cover of your water heater. Then contact a certified electrician to fix your home's electrical problems.

Secondly, you will get no or too little hot water if you activate holiday mode. In vacation mode, the controller maintains a tank temperature of 60°F. I recommend you to first check whether the device is in vacation mode or not. When this mode is activated, the holiday timer is displayed.

In this case the solution is simple. Just choose a heating mode like thatHybridmodusor theelectric modeto disable vacation mode and get hot water out of the unit.

Third, a triggered ECO button is also responsible for the fact that no hot water is produced. The ECO or energy cut-off switch is a safety feature. It shuts off the power to your water heater when the tank water temperature gets too high. Personally, I suggest you check the ECO or reset button. To do this, proceed as follows:

  • Turn off the circuit breaker on your water heater.
  • Remove the top access panel.
  • Fold away the insulation to access the ECO or reset button.
  • Press the button and you will hear a click indicating you have reset the ECO switch. If you don't hear a click, the reset button is not triggered. Regarding this, consult a professional to check your hybrid water heater.
  • Reinstall the insulation and top access panel.
  • Turn on the water heater circuit breaker.

Fourth, consider changing the heating mode when the hot water consumption pattern exceeds the capabilities of a particular heating mode. It is better to install a water heater that meets your needs.

And finally, a defective top heating element will result in your water heater not producing hot water. You should check the heating element electrically. To do this, turn off the circuit breaker, remove the top access panel, and fold away the insulation. Now remove the wires from the thermostat. Next, use a multimeter and place its probes between the two screw terminals on the top heating element.

A healthy heating element should read between 5 and 25 ohms. If the element resistance is outside of the acceptable range, you will need to replace the upper heating element. In this regard, this video will help you to replace the defective heating element:

02. Dripping from T&P relief valve

A small amount of water dripping from the T&P relief valve indicates either excessive water pressure or the tank is overheating. It turned out that debris stuck in the T&P relief valve was causing the valve to not seat properly. As a result, water will drip from the T&P relief valve.

How to fix:

The water pressure should be between 50 and 60 PSI. If the water pressure exceeds the range, you must install a pressure reducing valve on the cold water supply line. Then adjust the water pressure between 50 and 60 PSI.

If dirt is stuck in the T&P valve, you should remove the dirt. In this case, manually operate the T&P valve to clear the clog.

If the T&P relief valve is still dripping, you will need to hire a qualified plumber to replace the valve. Alternatively, watch this video if you're mechanically inclined to learn it yourself:

03. Water smell

Tap water contains harmless bacteria that can multiply when the water goes into the water heater, leaving a "rotten egg" smell. You can easily solve this problem by following the steps I will mention in How to Fix it section.

How to fix:

Setting your water heater to a higher temperature like 140° can kill the bacteria that cause odor. Also, you can install thermostatic mixing valves at each point of use to reduce the bacteria. And finally, you can replace the existing anode bar with a special zinc bar to eliminate odors.

(Video) How To Disable 48hr Default Mode Setting | A.O. Smith HP10 50H45DV

04. Water heater sounds

AO Smith Hybrid Water Heater Noise! Some kind of noise is normal as it is the water heater operating noise. In general, you may hear the sound of your water heater for the following reasons:

  • Normal expansion and contraction of metal parts during heating and cooling
  • Deposits on the bottom of the tank or around the heating elements
  • The operating noise of the fan or compressor of the heat pump

How to fix:

It is normal to hear some noise during heating and cooling due to the expansion and contraction of metal parts. In addition, the noise of the running heat compressor is also normal. So you don't have to worry. In any case, you don't have to take any steps to stop these noises.

But if you hear an unusual noise from the heater, I'll bet it's due to sediment buildup. In this case, you will need to drain or flush the unit to remove scale deposits from the bottom of the tank. Follow these steps to drain the device:

  • Turn off the circuit breaker on your water heater.
  • Open a hot water faucet to run the hot water until it gets cold.
  • Connect a garden hose to the drain valve and run the other end to the nearest floor drain or outside.
  • Turn the cold water supply valve to the off position.
  • Now open the drain valve and let the water drain out. To speed up the emptying process, you can open a hot water tap.
  • When you have drained the tank, remove the garden hose and close the drain valve. Don't forget to check the condition of the anode rod. Replace if necessary.
  • Finally, fill the water tank with water. You should never turn on the power before you have filled the tank. Otherwise the heating element will burn.

05. Temperature too high

A faulty thermostat or shorted heating element can result in water that is too hot. It is likely that the heating element will short out if the T&P relief valve is releasing a large volume of hot water. Also, if you turn the UIM setting higher, you will get too hot water.

How to fix:

You need to replace the non-working thermostat or the burned out heating element to solve the hot water problems. I recommend that you hire a qualified installer to replace these two parts if you are not mechanically inclined.

Also, don't forget to set the temperature on the UIM (User Interface Module). You can easily adjust the temperature with the up and down button. In this case, you should press the down button to reduce the temperature.

06. Low water pressure

Low water pressure is also a common problem with water heaters. It occurs because:

  • A melted dip tube
  • The water heater supply valve may be partially closed

How to fix:

First off, I recommend you check both the cold and hot water at a sink to make sure the lower pressure is only on the hot water side. If both sides have lower pressure, it's time to call your local utility company.

On the other hand, if the lower pressure problem is due to a melted fork tube, you will need to replace it. The following tutorial will help you replace the dip tube on your AO Smith Hybrid Water Heater:

You can also read: Replacing the Rheem fork tube.

Lastly, check the water heater supply valve. You must keep it fully open to maintain optimal water pressure.

07. Insufficient hot water

You are getting tepid or insufficient hot water from your AO Smith Hybrid water heater because of the following reasons:

  • Defective thermostatic mixing valve
  • Temperature setpoint too low
  • Reversed water connections
  • Leak in the plumbing system
  • Lower heating element without function
  • Dirty air filter

How to fix:

(Video) A.O. Smith Water Heater Complete Repair Guide - Includes Error Codes and Troubleshooting

Start by checking the faucets. Make sure it doesn't have a defective mixing valve. If the mixing valve becomes defective, it will reduce the water temperature even though there is enough hot water in the tank.

Next, check the water temperature point and adjust the temperature if necessary. To set the temperature, simply go to the user interface module and press the up button to increase the water temperature.

Third, check the water connections and make sure they are not reversed. If this is the problem, you need to disconnect and reinstall correctly.

Fourth, make sure there are no leaks in the plumbing system. It is better if you hire a plumber to inspect and repair the plumbing system.

If the bottom heating element is not working, you should replace it with a new one to restore your water heater to normal condition.

Finally, check the air filter on your hybrid water heater. Turn off the power before inspection. Then grasp the two tabs on the air filter and slide it out of the top cover of the unit. Next, take it to your sink and rinse it out to remove dirt and debris.

Then dry the air filter with a towel. When the air filter breaks, you need to replace it. Finally, put the air filter in place and turn the power back on to your water heater.

AO Smith Hybrid Water Heater Error Codes

Your AO Smith Hybrid Water Heater may be displaying some diagnostic codes. Below I will reveal the meaning of these error codes and show you how to clear them.

Error code "ICE" or "HPO"

If your water heater displays the error code 'ICE', understand that the heat pump is in a defrost cycle. On the other hand, the "HPO" troubleshooting code indicates that the ambient temperature is <45°F or >120°F and the average tank temperature is 59°F or less.

Fortunately, if the display shows these codes, you don't have to worry because it's normal. In short, you don't need to take any corrective action.

Error code "EUC"

The Hybrid Water Heater will display the error code “EUC” if the top heating element is faulty. Replacing the top heating element is the only way to solve this problem. If you don't know how to replace the top heating element, check out this tutorial:

ELC error code

ELC on your hybrid water heater display indicates that the bottom heating element is not working properly. So you only need to replace the bottom heating element. Check the manual and follow the instructions to change the bottom element successfully.

Error code "SF"

If your water heater's air filter is dirty, the error code 'SF' will appear on the display. To clear this error code, simply remove the air filter from the device and clean it. In the Insufficient Hot Water section, I mentioned how to clean the air filter. So go back to this section and learn how to do it.

Error code "ECF"

Your unit will display the error code "ECF" if the heat pump's compressor is running and stops frequently. The corrective action you should take is to call a professional if the compressor is running but the fan is not. Cleaning the air filter can also help you a lot in clearing this code. Finally, check the manual and make sure you meet the requirements for installing the heater in a confined space.

Error code "E20-E60"

If the display shows the error code "E20, E21, E30, E31, E50, E51, E10, E11, or E60", understand that there is a problem with the temperature sensor. To clear these error messages, I highly recommend you hire a professional.

Error Code "Edr"

Edr indicates that there is not enough water in the tank. To clear this error message, you should open and run all hot water faucets until the water flows continuously. Then fill the tank with water.

(Video) AO Smith Heat Pump Water Heater and Pump

EPL error code

The water heater will display the EPL error code when the supply voltage is too low. I suggest you call a certified electrician to check your home's electrical wiring and fix the problem.

Error code "EDH"

If the compressor discharge temperature gets too high, the device will give the error code “EDH”. To resolve this issue, you should call Residential Technical Support.

Error code "EoF"

EoF stands for condensate management. This error code appears for several reasons:

  • The device is not just installed
  • The primary or secondary condensate drain is clogged
  • Pump outlet tube clogged

Once you fix these issues, the code will disappear. If the problem persists, call the AO Smith technical support team.

ECL error code

If the heat pump suction pressure gets too low, your water heater will give an error code 'ECL'. And you should call AO Smith technical hotline to clear this error code.

ECC error code

A non-working heat pump compressor is the culprit that is causing your hybrid water heater to throw the ECC error code. Unfortunately, it's not a DIY task. In other words, you should call a professional to solve this water heater problem.

How do I reset the AO Smith Hybrid Water Heater?

Follow these steps to reset your AO Smith Hybrid Water Heater:

  • Turn off power to the device at the circuit breaker.
  • Use a flathead screwdriver to unscrew the top access panel.
  • Fold away the insulation to access the thermostat.
  • Once you remove the insulation you will see a round red button known as the ECO or reset button.
  • Press the button and your AO Smith Hybrid Water Heater will reset successfully.
  • Replace both the insulation and the top access panel.
  • Flip the circuit breaker up and turn power back on to your water heater.


Nothing is more annoying than a non-working water heater in the freezing cold winter days. When the water heater is to blame, every household chore seems to get stuck. We can't shower, wash dishes and so on because the water gets freezing cold.

Luckily, I've broken down all of the common issues you're encountering or already having with your AO Smith Hybrid Water Heater. So follow our guideline and take the steps I mentioned to solve a specific problem and get hot water to bring comfort back into your life.

Also read:

  • AO Smith Electric Water Heater Troubleshooting
  • AO Smith water heater thermostat problems
  • AO Smith water heater will not heat

AO Smith Hybrid Water Heater Troubleshooting [Complete Guide] (1)

Eric Alvarez

Eric Alvarez is an HVAC professional from El Paso, Texas, USA. He received his Bachelor of Science from the University of Texas at El Paso. Years of HVAC experience have taught him many lessons, not least that the value of quality and knowledge far exceeds any promised initial savings. He has a solid reputation for superior skills in heating, air conditioning, hot water tanks and indoor air quality systems.

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