Eternal Water Heater Error Codes [6 Easy Solutions]

Your eternal water heater may have been working just fine for years but now error codes are popping up. If you are getting error codes frequently, it may mean there is something wrong with your heater. 

Don’t panic yet! We’ll explain to you why all the common eternal water heater error codes happen and how you can solve the issue easily. So keep on scrolling to see what is wrong with your heater. We’ll fix it together! 

6 Eternal Water Heater Error Codes [Easy Solutions]

These are the 6 error codes most eternal water heater users complain about. We’ll go through their causes and the most reliable and easy way of fixes. 

For any of the error codes, the first thing you should try is turning the heater off and switching it back on after 5 minutes. If that doesn’t work for you, try the other fixes we’ll discuss for each error code.

Eternal Tankless Water Heater Error Code e02

This error code is displayed when your unit isn’t firing up. The reasons behind the heater not igniting are the flame signal not detected by the heater due to low gas supply, insufficient airflow, or issues with the ignition plug or wire.


Here are the things you need to check. One of them is usually the issue. 

  • First ensure that the gas line, igniter, and flame rod are working properly and there isn’t an issue with them.
  • There is an 8p wire and an igniter wire on your unit. Check whether their connections are secure.
  • Listen to the ignition noise. If there is any irregular sound, you may need to get it checked by a professional.
  • If so far, everything looks good, check the gas type and manifold pressure. 

Eternal Water Heater Error Code e03

This error occurs when the system loses the combustion signal after its detection. This combustion abnormality takes place when the mixture of air and fuel is improper. It can also be caused by an insufficient supply of gas or if there is any debris in the fan motor or fuel vent.


This issue is serious and if you don’t have any plumbing experience it would be better to contact a licensed plumbing contractor. The things that you’ll need to have a careful look at are-

  • Whether the gas supply is sufficient
  • The gas pressure, gas type, dip switches, and venting length. Ensure that there aren’t any issues with them.
  • The gas valve system
  • The wire connection of the igniter wire and 8p wire
  • You’ll also need to look at the power supply to check if your heater is getting the proper voltage.

Eternal Water Heater Error Code e24

This problem occurs when the mixing control valve is not connected.


This issue is simple to fix. Here’s what you need to do-

  • The mixing control valve makes a noise when in movement. Check to see if you can hear it.
  • Secure connection of the 160 wire and mixing valve wire.

The error code should no longer be there.

Eternal Tankless Water Heater Error Code e27

Eternal water heater error code 27 is caused by a mixing control valve initialization failure. When your mixing valve doesn’t initialize correctly e27 will be displayed by the heater.


Here are the steps you’ll need to take to check this issue. If you have no experience, we’d recommend you call in a professional.

  •  Start by draining the tank
  • Removing the metal clips that hold the valve in place, loosen the valve to disconnect the two cables.
  • There are two screws that you can spot holding the servo stepper motor sturdy. Take them out.
  • Now, be very gentle and release the four tabs to crack the motor open. This step requires a lot of care to avoid damaging the unit.
  • Remove the three cogs.
  • If you spot water in there, dry it out with a hairdryer or absorb the water with something.
  • After everything is dry, reassemble. 
  • Close the drain and air inlet valves.
  • Open the inlet and outlet water valves.
  • To allow air to leave the system, open a faucet.
  • After checking for leaks, close the unit and turn it on.

If the error persists, you have to get a valve replacement.

Alternatively, you can watch the video given below to fix your water heater e27.

Eternal Water Heater Error Code e28

This error is displayed when the power line of the main gas valve is open. If your filter or exhaust is plugged in by debris, this error will be displayed as well. 


  • Check the thermostat, the thermal fuse, and the air pressure switch for any issues with them.
  • Check to see if the thermostat, gas valve, thermal fuse, and air pressure switch wiring are secured tightly.
  • If there is nothing wrong with any of these, you have to take the unit apart. Inspect to see whether there is a blockage in the condensation drain line or any other part of the filter.
  • If that doesn’t fix your issue, you need to hire a professional or replace parts.

Eternal Water Heater Error Code e54

This error code indicates a current leak in the gas valve power.  


You have to check the gas valve and the connection of the gas valve wire. You’ll need a multimeter. Here are the steps to do that-

  • Turn off the unit and wait for it to cool down.
  • There are bolts in the service panel that is on the side of the furnace. Take them out.
  • Locate the gas valve. There are two wires on its top or side that are clipped to the solenoid terminals.
  • Keep note of where the wires are attached before removing them.
  • Take the multimeter. Turn the test control to “mV” or millivolt. 
  • Press the multimeter tester wands on the terminals on the gas valve. If the reading is in the range of 145-195 mV, it is normal.
  • If you get a reading outside this range, you have to replace the gas valve.

Eternal Tankless Water Heater Tech Support

If you need any other information about your eternal water heater, you can contact their customer support team. They take calls from 8 am-4 pm CST, Monday through Friday.

Here is their number: 1-866-946-1096. You can also arrange a service call with the service agent nearest to you.


Who makes eternal water heaters?

A manufacturing company in Taiwan, called Grand Hall used to make eternal water heaters. The company is no longer in business. 

Can you run out of hot water with a tankless water heater?

A tankless water heater heats water on demand. So, you’ll not run out of hot water as water is heated instantly with this type of heater. 

What is the best temperature to set a tankless water heater?

The optimum temperature that I’d suggest you try is between 100-115 degrees Fahrenheit. Find what suits you best in this range with some experimentation.

What size tankless water heater do I need for a family of 5?

That depends on the weather. For example: If you live in the Northern part of the USA, where the temperature is lower, your heater has to work extra hard. If you live there, I’d say, a 10 GPM gas tankless heater or 27 kW is best.

Why is tankless water heater installation so expensive?

A tankless water heater needs a larger gas supply and it also needs to run the exhaust flue to the exterior on its own. Because of that, it costs more money to install a tankless water heater.


Our guide should solve the more common issues faced by eternal water heater users. But, there are many more error codes that can occur in an eternal tankless water heater. 

If you need any further queries, you can comment down here. We’ll try our best to help you out.

About William

William is the founder of He has real life practical skills in fixing smoker & heating appliance issues. He loves to share his knowledge & helps others in fixing their appliances & saving their money. William firmly believes that anyone can repair his or her unit with the correct guidance & knowledge. See more at about us.

6 thoughts on “Eternal Water Heater Error Codes [6 Easy Solutions]”

  1. Hi, I have error code E28. I keep reading to check the Air pressure switch, thermal fuse and thermostat. The only part I can find is the air pressure switch. I have a whole spare machine that I can swap all these parts if I only knew where the thermal fuse and thermostat is. Can you point them out? they are not in any parts diagram that I can find. thanks

    • Hi Laurie

      It would be wise to take a look at the system’s user guide that can help you to locate the thermal fuse and thermostat. It’s because the thermal fuse and thermostat location can vary from model to model.


  2. I do not have an error code. However, I just flushed my system and now my popoff valve is getting hot. I can not see the end of the pipe as it goes directly into a drain. I can’t hear any water coming out either.
    What would cause this, how can I fix it and will it hurt my pipes and / or pipe joints?
    I do not have an owner’s manual. The plumber did not leave me one when we built the house.
    Your help would be appreciated.


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