Why Water Heater Keeps Going Into Vacation Mode [Solved]

The major reasons for water heaters to keep going to vacation mode include building up carbon in the flame sensor or the insulator of the flame sensor that has been cracked. If fixing the flame sensor is not proving well, it is sure the gas control valve is the leading reason for this issue.

water heater keeps going into vacation mode

While you are moving through to fix the stuck vacation mode issue, first concentrate on the flame sensor, and clean the carbon build-up from the sensor. 

Plus, check if the insulator of the sensor has been cracked or not and replace it. If all above aren’t able to resolve the issue, you need to replace the faulty gas valve. 

Scroll down to learn in detail.  

Why Water Heater Keeps Going Into Vacation Mode [Solved]

Read through our comprehensive guide to know about water heater vacation mode and how you will handle the water heater that keeps switching to this mode.

Note: You can also read how to fix the Honeywell water heater sensor failure.

Water Heater Vacation Mode- What is it

The vacation mode is an important setting on the water heater system, which allows the heater to run at a lower temperature. In this feature, the pilot light will keep going on, but it will no longer heat the water due to lowering the temperature. 

The feature is quite helpful, especially when you are not using the heater for a longer period of time. This setting will save you from consuming energy more than usual, and it will save you money. 

Apart from them, by dropping the water heater’s temperature, it will keep water flowing and prevent the pipe from freezing while powering it with just enough energy. 

If you are not using the vacation mode, the heater will continue using the same amount of energy as before. This will increase the heating bill unnecessarily or may occur various damages to the system. 

What Is The Purpose Of Using Vacation Mode In Water Heater

There are a few good sights of setting vacation mode on your water heater. Let’s have a glimpse at some of the advantages of this nice energy-saving feature:

  • Saves Money: The best thing about the vacation mode feature is saving enough money of yours. In this mode, the heater keeps the temperature under 120 degrees. This lessens the amount of energy needed by the water heater, which reduces your energy bill. 
  • Eco-friendly: Almost all water heater uses fuel like gas or electricity to heat the water. But in vacation mode, the system lowers the temperature, which reduces the energy resource consumption for the most part. This will prevent in depleting the energy resources.
  • Prevent System Damage: The water heater not only reduces energy consumption but also lowers the full-blown operation of the heater. As the water heater is not in full operation, the risk of building up minerals inside your heater’s plumbing will be decreased.

Also, the long-running water heater may wear out the water heater components. So, activating the vacation mode saves the component from wearing out and keeps efficiency by preventing frozen plumbing.

Reasons Why Hot Water Heater Keeps Going To Vacation Mode

Here we have included all the responsive factors for occurring stuck vacation mode issue on hot water heater and all the well-proven solution procedures:

1. Carbon Build-Up In The Flame Sensor

If your hot water heater keeps going to vacation mode, it is sure that the flame sensor is the leading culprit. The flame sensor might stop working due to carbon buildup on it.

carbon build-up in the flame sensor

A flame sensor is a crucial safety component in hot water which control gas flow in gas water heaters. During an ignition cycle, a hot surface igniter creates sparks to ignite the gas. 

Once the gas is ignited, the flame sensor converts it into an electrical current, which will work as a switch to control the gas flow from the gas supply valve.

This essential element may be clogged with carbon buildup, dust, and other debris. Due to carbon buildup, the sensor fails to sense the correct temperature of the heater.

Here, it will detect low-wavelength light instead of high-wavelength light set at higher temperatures, which refers to vacation mode. This happens when the sensor reads low temperatures, assuming that the water heater should go into vacation mode.

The only solution is cleaning the heavy carbon build-up from the sensor. 

How To Clean The Flame Sensor On The Hot Water Heater

  • To clean the flame sensor, you will need steel wool or 60-grit sandpaper, emery cloth, and a microfiber towel. 
  • Now, start by disconnecting the gas supply to the heater.
  • Locate the flame sensor inside the burner assembly. So, grab the burner supply tube and remove it from the burner combustion compartment. 
  • Remove the flame sensor from its mounting bracket.
  • Take the grit sandpaper and clean the stubborn stains from the sensor body.
  • Remove any excess dirt buildup on the sensor using the microfiber towel.
  • Once the sensor has been cleaned, place the sensor back in place and reassemble the heater.

2. Faulty Water Heater Flame Sensor

After cleaning the dirty flame sensor of the water heater, and still, the heater is switching to vacation mode, be sure the faulty flame sensor is now the culprit. 

faulty water heater flame sensor

The sensor is secured with porcelain or insulation around it. The higher possibility is the insulator of the sensor has been cracked. This part is responsible for heat detection. 

Due to cracked insulation, the sensor will stop working and fail to sense the accurate temperature, leading to vacation mode.

Once you have detected a crack in the outer porcelain part, you need to replace the complete flame sensor. Replacing the bad flame sensor is relatively straightforward. 

The following tips will help you to replace the flame sensor from your furnace. 

How To Replace The Flame Sensor On A Hot Water Heater [Simple Steps To Follow]

  • First, turn off the hater and shut off the gas supply.
  • Remove the burner assembly manifold cover.
  • Then unscrew all the attached screws and pull out the burner assembly from the burner combustion compartment.
  • Remove the old gasket through the manifold cover plate to release the burner tube.
  • Now, pull and twist the old flame sensor from its mounting bracket. Then, disconnect the sensor by pulling it through the rubber grommet seal from inside to outside.
  • Now take the new sensor and insert it from the outside through the grommet.
  • Install the sensor to its mounting bracket and ensure it is fully seated or clicks into place.
  • Finally, reinstall the burner unit and turn on the gas supply.

3. Defective Gas Control Valve

Well!! You have already replaced the faulty flame sensor from your heater. But if you are still troubled with vacation mode on the gas water heater, it could be a defective gas control valve. 

The gas control valve mainly controls the gas supply to the pilot and allows the pilot to be lit. Then the lit pilot heats the water heater thermocouple, and the water starts heating. The valve also controls the water temperature of the heater.

So, if the valve stops working, it will fail to regulate the temperature, and for this, the heater will go into vacation mode constantly. You will need a new gas valve to change the stuck temperature.


The only solution is to replace the bad gas control valve from your heater. Replacing the gas valve on a hot water heater isn’t as hard as it may seem.

But if you want to replace it quickly and safely, it will be better to contact a professional plumber to replace the defective gas control valve

After replacing all the above defective parts, we can hope you are no more struggling with the stuck vacation mode of your water heater. 

How To Set The Water Heater To Vacation Mode

Most water heaters have already featured a “Vacation Mode” function, from which you can activate the mode. Otherwise, you can set it manually from the thermostat setting. 

thermostat setting into vacation mode

Learn some of the effective methods to set the water heater into “Vacation Mode”:

  • Go to the thermostat dialer of your water heater. Turn the dial to the “Vacation” setting if you see a vacation mode in the menu.
  • If your dial menu has no vacation option, just turn it to the “Pilot” setting. It will keep the pilot on but prevent the burner from coming on when there is no need for heating water.
  • There is another method that you may follow to set your heater in this mode. Just lower the temperature to 50 degrees Fahrenheit or any lowest setting of the thermostat. It will do the same thing a vacation mode would do. 

How To Get Water Heater Out Of Vacation Mode

Follow the below instructions to get your water heater out of vacation mode:

  • If the water heater features LCD touch controls, first make sure it is unlocked.
  • In the case of locked LCD touch controls, press and hold the “UP” and “DOWN” buttons for 3 seconds. It will unlock the controls.
  • Now, locate the vacation button from the right of the “UP” button.
  • Press and hold the “Vacation” button for about 3 seconds. Your unit will exit from vacation mode.
  • If your unit has a temperature dialer instead of LCD touch controls, simply turn the dialer higher than 120F to exit vacation mode.

Do Bacteria Grow In Water Heater Vacation Mode

There is the most common query about “water heater vacation mode bacteria”. 

There are a few bacteria that may grow in your water heater. Legionella is the most common among them. 

Legionella is such bacteria that causes Legionnaires’ disease. Legionella never thrives in cold water. Lukewarm water or water heated below 108 degrees Fahrenheit encourages Legionnaires’ growth. 

The vacation mode keeps the pilot light on but keeps your water tank cold. One who inhales microdroplets of legionella-contaminated water easily gets attacked with Legionnaires’ disease, which is a severe type of pneumonia. Also, it can cause lung inflammation, head and muscle aches, bloody coughs, and sometimes chest pain. 

Considering this, it’s important to make sure about killing the bacterial growth before using the hot water set in vacation mode. For that, turn the water heater back on and set the temperature above 120° F. It will kill the Legionella bacteria. 

The Legionella bacteria’s actual disinfection range is 158 – 176 ° F. So it will be better to set the temperature at 140° F, in which Legionellae dies in 32 minutes. 

Plus, a study from the American Society of Sanitary Engineering, setting water heater temperatures between 135 and 140°F is highly preferable to stop the growth of the legionella bacteria. 


What if my water heater smells like rotten eggs?

If your water heater smells like rotten eggs, there is a higher chance of bacterial issues. They are invisible, but the lower temperature encourages their growth. So, raising the water temperature will destroy the bacteria, and your heater will stop that smell.

Does my water heater temperature change on its own?

Yes!! The water heater temperature can change by itself when the cold water circulates into it. Also, it can be changed due to a lack of proper maintenance or if you have an old water heater.

Wrapping Thoughts:

Well!! That’s all we have!! Our above-assembled guide is enough to resolve the “AO Smith water heater keeps going into vacation mode” issue or any hot water heater vacation mode problems. 

We can hope now you have no more queries about this fact, and you will fix your unit issue by following our guide. 

Still, if you face any troubles while fixing the issue, let us know through comments. We are always here for you.

About William

William is the founder of Fireplacehubs.com. 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.

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