AO Smith Hybrid Water Heater Troubleshooting

AO Smith Hybrid Water Heater Troubleshooting [Complete Guide]

This is a complete guide on AO Smith Hybrid Water Heater Troubleshooting. In this article, I am going to break down: 

  • 7 Common Hybrid Water Heater Problems
  • Reveal the meaning of every AO Smith Hybrid Water Heater error code 
  • How to reset your AO Smith Hybrid Water Heater?

Without further ado, let’s dive in. 

Table of Contents

AO Smith Hybrid Water Heater Troubleshooting [7 Common Problems]

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

01. No Hot Water

Some common reasons for an electric or hybrid water heater to deliver no hot water are: 

  • Unit gets no electric power
  • Water heater is in vacation mode 
  • Eco or reset button gets tripped
  • Hot water usage pattern may cross the capability of the unit in current mode
  • Defective upper heating element
  • Leak in plumbing system. 

How To Fix: 

Begin with checking whether the water heater gets electric power or not. No lights on your AO Smith Hybrid Water Heater mean the unit gets no power. It occurs if there is a problem with your home’s electric wiring or circuit breakers.  

I highly recommend you get a non-contact circuit tester to test the electrical wirings. First, find the water heater’s circuit breaker and flip 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 power wires. On the other hand, the copper or green is the ground wire. 

Fourth, turn the circuit breaker on and check the two power wires using the non-contact circuit tester. If you get no power at your water heater, turn off the breaker again. Then, replace the junction cover of your water heater. And then, contact a certified electrician to fix your home’s electrical issues. 

Secondly, you will get no or insufficient hot water if you activate the vacation mode. In Vacation Mode, the controller maintains a 60°F tank temperature. What I recommend you is- first verify whether the unit is in vacation mode or not. If this mode gets activated, the vacation timer will be displayed. 

In this case, the solution is simple. Just choose an heating mode like the hybrid mode or the electric mode to deactivate the vacation mode and get hot water from the unit.

Thirdly, a tripped ECO button is also a culprit responsible for producing no hot water. The ECO or energy cut-off switch is a safety feature. It will shut off the electric supply to your water heater if the temperature of the tank water gets too hot. Personally, I suggest you check the ECO or reset button. To do this, do the followings: 

  • Turn the circuit breaker of your water heater off.
  • Remove the upper access panel.
  • Fold away the insulation to access the ECO or reset button. 
  • Press the button and you will hear a click, which indicates you reset the ECO switch. If you don’t hear a click, the reset button doesn’t get tripped. Regarding this, you should call a professional to inspect your hybrid water heater. 
  • Replace the insulation and the upper access panel. 
  • Turn on the water heater circuit breaker. 

Fourthly, you should change the heating mode if the hot water usage pattern exceeds the capability of a certain heating mode. It will be better to install a water heater that meets your demand. 

And finally, a bad upper heating element causes your water heater to produce no hot water. You should inspect the heating element electrically. To do so, turn the circuit breaker off, remove the upper 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 upper heating element. 

A healthy heating element should give a reading between 5 to 25 Ohms. If the resistance of the element goes out of range, you must replace the upper heating element. In this regard, this video will help you in replacing the bad heating element: 

02. Drips From T&P Relief Valve

A little amount of water dripping from the T&P Relief Valve stands for either there is too high water pressure or the tank gets overheated. Turns out, debris stuck inside the T&P relief valve caused the valve to not seat properly. Consequently, the T&P relief valve will drip water. 

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. 

For stuck-in debris inside the T&P valve, you should clear the debris. In this case, operate the T&P valve manually to release the blockage. 

If the T&P relief valve is still dripping, you must hire a qualified plumber to replace the valve. Alternatively, you can take a look at this video if you are mechanically inclined to learn how to do it yourself: 

03. Water Odor

Tap water contains harmless bacteria, which may multiply when the water goes into the water heater and leaves a ‘rotten egg’ smell. You can easily solve this issue by taking the steps I will mention in the below ‘how to fix’ section. 

How To Fix: 

Setting your water heater to a higher temperature like 140° can kill the bacteria that causes smell. Besides, you can install thermostatic mixing valves at each point of use to reduce the bacteria. And lastly, you can replace the existing anode rod with a specialized zinc rod to eliminate odor. 

04. Water Heater Sounds

AO Smith Hybrid Water Heater Noise! Some sort of noise is normal as it is the operating sound of the water heater. Generally, you can hear the sound of your water heater due to the following reasons: 

  • Normal expansion and contraction of metal parts during the period of heat-up and cool-down
  • Sediment build-up on the bottom of the tank or around the heating elements
  • The operating sound of fan or heat pump compressor

How To Fix: 

It’s normal to hear a noise during the period of heat-up and cool-down due to expansion and contraction of metal parts. Plus, the sound of the heat compressor running is also normal. So, you don’t need to worry about it. Either way, you need to take no steps to stop these noises. 

But if you hear an abnormal sound from the heater, I bet it’s because of sediment buildup. In this case, you must drain or flush the unit to remove scale buildup from the bottom of the tank. Go along with these steps to drain the unit:

  • Turn your water heater’s circuit breaker off.
  • Open a hot water faucet to let the hot water run until it gets cold.
  • Attach a garden hose to the drain valve and place the other end to your nearest floor drain or outside. 
  • Set the cold water supply valve to the off position. 
  • Now, open the drain valve and let the water drain. To make the draining process faster, you can open a hot water faucet. 
  • Once you drain the tank, detach the garden hose and close the drain valve. Don’t forget to check the condition of the anode rod. If needed, replace it. 
  • Finally, fill the water tank with water. You should never turn the electrical power on until you fill the tank. Otherwise, it will burn the heating element.  

05. Temperature Too High

A malfunctioning thermostat or shorted heating element can cause too hot water. It’s likely the heating element gets shorted if the T&P relief valve releases a large amount of hot water. Besides, you will get too hot water if you set the UIM setting higher. 

How To Fix: 

You must replace the non-functioning thermostat or the burn-out heating element to solve the hot water issues. I recommend you hire a qualified plumber to replace these two parts if you are not mechanically inclined. 

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

06. Low Water Pressure

Low water pressure is also a common water heater problem. It occurs due to:

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

How To Fix: 

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

On the other hand, if the lower pressure issue is the result of a melted dip tube, you must replace it. The following tutorial will help you in replacing the dip tube on your AO Smith Hybrid Water Heater: 

You can also read: Rheem Dip Tube Replacement.

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

07. Insufficient Hot Water

You will get lukewarm or insufficient hot water output from your AO Smith Hybrid Water Heater due to the following reasons: 

  • Defective thermostatic mixing valve
  • Too low temperature set point 
  • Reversed water connections 
  • Leak in plumbing system
  • Non-functioning lower heating element
  • Dirty Air Filter

How To Fix: 

Start with checking the faucets. Ensure it doesn’t have a defective mixing valve. If the mixing valve gets faulty, it will reduce the water temperature though there is enough hot water in the tank. 

Next, check the water temperature point and adjust the temperature if needed. To adjust the temperature, just go to the User Interface Module and press the up button to increase water temperature. 

Thirdly, inspect the water connections and ensure they don’t get reversed. If this is the problem, you must disconnect the connections and re-install them correctly. 

Fourthly, ensure there is no leak in the plumbing system. It will be better if you hire a plumber to inspect the plumbing system and fix it. 

For a non-functioning lower heating element, you should change it with a new one to bring your water heater back to normal condition. 

And lastly, check the air filter of your hybrid water heater. Before inspecting it, turn the power off to the unit. Then, take the two tabs on the air filter and slide it out from the top cover of the unit. Next, bring it to your sink and wash it out to clean dirt & debris. 

Afterward, towel-dry the air filter. If the air filter gets broken, you must replace it. Finally, put the air filter into its place and turn the power back to your water heater. 

AO Smith Hybrid Water Heater Error Codes

Your AO Smith Hybrid Water Heater may display some diagnostic codes. Below, I will disclose the meaning of those error codes and show you the way of erasing them. 

Error Code ‘ICE’ or ‘HPO’

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

Fortunately, you don’t need to tense if the display shows these codes because it’s normal. In short, you don’t need to take any corrective actions. 

Error Code ‘EUC’

The hybrid water heater will flash the error code ‘EUC’ if the upper heating element is at fault. Replacing the upper heating element is the only way to solve this issue. If you don’t know how to replace the upper heating element, check out this tutorial: 

Error Code ‘ELC’

ELC on the display of your hybrid water heater indicates the lower heating element is not functioning properly. So, what you need to do is- just replace the lower heating element. Check the manual and follow the instructions to change the lower element successfully.  

Error Code ‘SF’

When the air filter of your water heater gets dirty, it will alarm the error code ‘SF’ on the display. To clear this error code, just take the air filter out of the unit and clean it. In the ‘Insufficient Hot Water’ section, I mentioned how to clean the air filter. So, go back to that section and learn how to do it. 

Error Code ‘ECF’

Your unit will display the trouble code ‘ECF’ when the heat pump compressor is running and stopping frequently. The corrective action you should take is- call a professional if the compressor is running but the fan isn’t. Cleaning the air filter can also help you a lot to erase this code. Lastly, check the manual and ensure you meet the requirements in installing the heater in a confined space.  

Error Code ‘E20-E60’

If the display shows error code ‘E20, E21, E30, E31, E50, E51, E10, E11, or E60, understand there is an issue with the temperature sensor. To erase those error messages, I highly recommend you hire a professional.  

Error Code ‘Edr’

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

Error Code ‘EPL’

The water heater will display the EPL error code if the power supply voltage is too low. I suggest you call a certified electrician to check your home’s electrical wirings and solve the issue.  

Error Code ‘EDH’

When the compressor discharge temperature gets too high, the unit will throw the error code ‘EDH’. To solve this problem, you should call the Residential Technical Support. 

Error Code ‘EoF’

EoF stands for condensate management. This error code will pop up due to several reasons: 

  • The unit isn’t installed in level 
  • The primary or secondary condensate drain gets clogged
  • Pump outlet tube gets blocked

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

Error Code ‘ECL’

When the heat pump suction pressure gets too low, your water heater will beep the error code ‘ECL’. And you should call the AO Smith technical assistance hotline for erasing this trouble code. 

Error Code ‘ECC’

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

How To Reset AO Smith Hybrid Water Heater?

Stick to the below steps to reset your AO Smith Hybrid Water Heater: 

  • Turn off electric power to the unit at the circuit breaker.
  • Use a flat head screwdriver to unscrew the upper access panel. 
  • Fold away the insulation to access the thermostat. 
  • Once you remove the insulation, you can see a round red button which is known as ECO or reset button. 
  • Press the button and it will reset your AO Smith Hybrid Water Heater successfully. 
  • Replace both the insulation and the upper access panel. 
  • Flip the circuit breaker up and turn the electric supply back to your water heater. 


Nothing is more frustrating than a non-functioning water heater in the ice-cold days of winter. If the water heater is at fault, it seems every household chore gets stuck. We can’t take a shower, wash dishes, and so on as the water gets freezy cold. 

Fortunately, I broke down every common problem you will encounter or already go through 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 to your life. 

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One Comment

  1. I have one of these water heaters. I was told the default setting is 120 degrees. I would like to set it to 125 to 130 degrees as it is only warmish.
    how do I see a read out of the current temperature? how do I know what the temp is that it is set at. The digital read out is non existent. It is in Hybrid mode

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