State Select Water Heater Temperature Sensor Failure [Fixed]

The main reasons behind State Select water heater temperature sensor failure are:

  • Loose wiring connection of the sensor.
  • Dirt has accumulated on the sensor.
  • Bent, broken, or faulty sensor.

When the sensor fails, it won’t be able to control the gas control valve. So, your heater won’t work correctly. There are many things you need to know when dealing with a bad temperature sensor.

Luckily, I’ll cover it in this guide. Besides fixing the faulty sensor in gas heaters, you’ll also learn how you can do it in electric heaters. So, let’s dive right in!

State Select Water Heater Temperature Sensor Failure [Gas Units]

The water heater sensor is an important component in regulating the hot water temperature. As it controls the gas valve, you’d face many issues with your water heater when you have a bad sensor.

state select water heater temperature sensor failure

Before diving deep into how you can fix a faulty sensor, you need to know why a sensor fails in the first place. There are many potential reasons why your sensor can fail. Here are the most common ones:

1. Heater Is Old

Your heaters aren’t meant to last forever and neither are the components inside them. If you have been using your heater for longer than a decade, it’s normal that some components will start to wear out. The temperature sensor is no exception and can get damaged simply by outliving its utility.

state select old gas water heater

2. Physical Damage Or Corrosion

As your temperature sensor is always around the presence of water, it can get corroded with time. The quality of the water in your area plays a major role in how quickly the sensor wears out. If you have hard water in your area, the sensor will get corroded much quicker.

The sensor can also be damaged if you have moved the heater recently. Mishandling the heater during either maintenance or repair or relocation can lead to a failed sensor.

3. Electrical Problems

The temperature sensor is an electrical component as it sends a small amount of current during its operation. If there are any abrupt voltage spikes or electrical surges, it can damage the sensor. 

Those were the main reasons that would make a temperature sensor go bad. If you suspect that you have a bad sensor, you need to be sure that it’s bad before you replace it. I’ll walk you through how you can execute this entire process only by following a few easy steps.

First, I’ll look at the common symptoms of a bad sensor. Then, I’ll see how you can test the sensor with a multimeter to rule out any other issues. That’ll confirm if you have a bad sensor.

If the test reveals that you have a bad sensor, you’ll have to replace the sensor. We have dedicated sections on all these topics. So, keep on reading to learn more about this issue and its fixes.

How To Tell If The Sensor Is Going Bad

I’ll look at the primary signs of having a bad sensor in this chapter. If you notice any of these symptoms, you need to move on to testing the sensor. For now, here are the main signs of a bad sensor:

1. Water Isn’t Hot Enough

The main job of the temperature sensor is to regulate the water temperature. It’s obvious that there will be issues with the water temperature if the sensor goes bad. So, if your water doesn’t get hot enough, it could be due to a bad temperature sensor.

state select water heater water isn’t hot enough

Keep in mind that there are also other issues that can lead to you not getting enough hot water. For example, setting the thermostat low can also give you lukewarm water.

Similarly, damaged thermostatic mixing valves, using an undersized water heater, and the pilot not staying lit can also cause this issue.

The first thing you should do is check the pilot light. Look through the viewport in your heater to see if the pilot is styling lit. If the pilot isn’t lighting up, check out our State Select pilot light troubleshooting guide to fix the issue.

If the pilot light is fine, it could be due to other issues with your gas water heater as mentioned. In that case, you can check out our troubleshooting guide on State Select gas water heaters to solve those issues. If the problem still remains, there’s a good chance that you have a bad temperature sensor.

2. Water Is Too Hot

A bad temperature sensor will mess up the water temperature. It can go either way – the water temperature may not get hot enough or it can get too hot. Without a doubt, the water getting too hot is more dangerous as it opens you up to the risk of scalding.

If you’ve set the thermostat too high, that can also cause this issue. A faulty gas control thermostat could cause this problem as well. Check out our guide on replacing State Select thermostats to find out how you can diagnose and replace them if needed.

If there are no issues with the thermostat and it’s functioning properly, the main culprit here is most likely the thermistor. If it has gone bad, you’ll have to replace it with a new one.

3. Temperature Fluctuations

When you have a bad temperature sensor, the water heater can become active and inactive abruptly. So, you’d got inconsistent temperatures from your water heater. It can be extremely annoying to get bursts of cold water during a hot shower. But it’s a strong sign of having a bad thermistor.

4. Failed Gas Control Valve

The temperature sensor sends a signal directly to the gas valve to manipulate what it does. When you have a bad sensor, it can give incorrect signals and the gas control valve could completely fail.

state select water heater gas control valve

5. Status Light Flashes 5 Times

The first major warning sign of having a bad sensor is when the status light flashes 5 times. It’s an error code designed to indicate that the temperature sensor has failed.

state select water heater status light

When you see this error code, it usually means that the thermistor is faulty and needs to be replaced. But it could also be due to the wiring being loose. So, if the wiring is tight, it’s definitely the thermistor that’s causing the issue.

Inspect the wiring first. If everything checks out with it, then you can conclude that you have a bad temperature sensor and you can replace it.

How To Test The Temperature Sensor

I’ve talked about the symptoms of a bad temperature sensor failure. But there are other issues that can cause those symptoms too. So, the only sure-shot way of knowing whether you have a bad temperature sensor is to test it using a multimeter.

If you test the temperature sensor, there’ll no longer be any confusion about whether it’s bad or not. You can easily move on to replace it if the test reveals that you have a bad sensor.

Before you move on to testing the sensor, make sure the wiring attached to it is secure. Loose wiring can also cause issues with the temperature sensor. Once you’re sure that there are no issues with the wiring, you can follow these steps to test the thermistor:

  • Get pin probes that you can insert into the small holes of the temperature sensor. Using regular probes can destroy the temperature sensor. So, collect the right pin probes to test the sensor.
  • Set the multimeter to the lowest Ohm settings and connect the multimeter to the pins inside the plastic connector of the temperature sensor. Make sure you push the pins thoroughly and collect the readings of the resistance.
  • On some models, you may have to disassemble the gas control valve to access the temperature sensor. If you have to do it in your heater, unscrew the gas valve but make sure that the temperature sensor is connected to the black plate of your water heater. Then, collect the resistance readings.
  • Measure the water temperature. Look at the right resistance based on your manufacturer’s chart. If the reading you got matches that, it means your temperature sensor is okay. If the reading is outside the specified range, you have a faulty temperature sensor and it’ll have to be replaced.
  • If the temperature sensor is okay, there’s a strong chance that the gas control valve is bad. You’d have to replace it in that case.

When you take the readings, make sure you’re being accurate. Don’t round off the results as it can skew the results. Now you know how to test the temperature sensor in your State Select gas water heater. 

How To Fix The Faulty Hot Water Sensor Issue

When you have a bad temperature sensor, you have some options. The first thing you should do is power cycle the heater. It can restore the heater to normal operation in a few cases. Power cycling the heater can also be a temporary solution while you’re waiting for the replacement to arrive.

The second option is to clean the temperature sensor. If the sensor is only dirty and not damaged, cleaning it will work. But the ideal and long-term solution here is to replace the sensor altogether. Those are your three options. Now, let’s look at each of them in detail.

01: Power Cycle The Heater

Power cycling the heater will get rid of minor glitches in the heater. You should do this practice once in a while as a maintenance act for your heater. Follow these steps to do it:

  • Turn the gas control knob to the “Off” position and remove the outer door of your water heater. Leave the water heater in this condition for about 10 minutes so that the gas inside the heater can spread out.
  • Then, you have to relight the pilot. Turn the gas control knob to the “Pilot” position and press the button inwards. While holding the pilot button down, keep clicking the igniter. Do it for at least 90 seconds.
  • There will be no status light in your State Select water heater if the pilot doesn’t light. And the status light will start to flash indicating that the pilot is lit. Confirm whether the pilot is actually lit by looking at it through the viewport. If it’s lit, you can set the heater to your desired temperature and use it.

If the pilot doesn’t light up right away after your first try, you can give it to 2-3 more attempts. Make sure there are at least 10-minute breaks between each attempt to clear out the gas. If you can’t still light the pilot, you can consult a technician to solve the issue.

02: Clean The Sensor

As you know, the sensor can just be dirty instead of damaged. If that’s the case, you need to clean it. Just locate it, take it out, clean it, and put it back in its original place.

state select water heater temperature sensor

Keep in mind that cleaning the thermistor isn’t a permanent fix as it can get damaged with time. Eventually, you’ll have to replace it. Cleaning it can only extend its lifespan for a while.

03: Replace The Temperature Sensor

If the test reveals that you have a bad water heater sensor, the permanent fix is to replace the temperature sensor. Keep reading to find out how you can do it.

How To Replace A Faulty Water Heater Temperature Sensor

If you have experience working with heaters, replacing the temperature sensor will be a breeze. But you have to arrange some tools to carry out the replacement process. Here are the tools you need:

  1. 11/32 Nut Driver
  2. T20 Torx
  3. ¾ Inch Wrench
  4. ⅜ Inch Wrench
  5. ½ Inch Wrench
  6. 7/16 Inch Wrench

Once you have your hands on these tools, you can follow these steps to replace the temperature sensor:

  • Shut off the gas supply. Disconnect the thermopile, temperature sensor, and igniter from the gas valve. Use the 7/16-inch wrench to disconnect the gas supply to the pilot light.
  • Use the ¾ Inch Wrench to disconnect the main gas supply. Remove the screws holding the burner door in place. Once that’s done, gently slide out the main burner assembly.
  • Loosen the temperature sensor using the wrenches and unscrew it. Place the new sensor in place of the old one and tighten it. Then, reverse engineer the above steps, install the main burner in its place and attach the gas valve connections. Turn on the gas to the heater and you’re good to go.

So, that’s how you can easily replace the thermistor on your own. If you’re not okay with doing it yourself, you can always hire a qualified technician to do the job. Either way, replacing the faulty sensor should fix your problem. Hopefully, you’ll get adequate hot water from your heater again.

State Select Hot Water Heater Sensor Failure [Electric Units: How To Fix]

The temperature sensor isn’t a component that you’d only find in gas heaters. They’re also available in electric water heaters and they’re also prone to going bad. There are usually two temperature sensors in electric heaters as there are two heating elements.

state select electric water heater

You can tell which one is bad by looking at the error code in your electric water heater. If there are 3 red flashes, it’s the upper-temperature sensor that has gone bad. If you see 7 flashes, the lower thermistor has gone bad.

Now, you know how you can tell which of the sensors has gone bad. So, how can you fix the problem? It’s simple – you have to replace the faulty sensor. 

If the upper thermistor goes bad, you’d have to replace the electronic thermostat to rectify the issue. The upper thermistor is a part of the thermostat. Just turn off the power to the heater by flipping the circuit breaker, replace the thermostat, and turn the power back on.

If the lower thermistor is faulty, you can follow these steps to fix the issue:

1. Turn off the power to the heater by flipping the breaker.

2. Check the wiring connections at Electronic Thermostat (ET) and make sure they’re okay. If there are any issues with the connections, fix them before moving on.

3. Replace the lower thermistor sensor with a new one.

4. Turn on the electrical power at the breaker.

So, that’s how you can fix the issue when the thermistors in the electric heaters go bad. Hopefully, the error code will disappear after you replace the faulty component and your heater will operate normally again.

State Select Water Heater Temperature Sensor Failure [Electric Tankless Units – How To Fix]

There are multiple temperature sensors or thermistors in State Select electric tankless water heaters. If you’re using a point-of-use model, you’ll see the flash code sequence 1-2 when the inlet thermistor is open. Similarly, you’ll see the 1-3 flashing sequence if the outlet thermistor is open.

state select electric tankless water heater thermistor

Besides that, the 1-4 error code represents that the water temperature has gone beyond 145°F. The heater will also display the 3-6 error code when it detects that the incoming water temperature is too low. To be precise, it’ll give this freeze warning when the temperature is lower than 40°F.

Both of these issues can also be caused by a faulty thermistor. There are even more thermistors in the two and four-chamber models. The error codes E10, E11, E12, E13, E14, E20, E21, E22, E23, and E24 indicate thermistor issues.

If you notice any of these error codes, you should check the wiring of the thermistor first. If the wiring has come loose, tighten its connection to the thermistor in question. If that still doesn’t work, you’d have to replace the thermistor with a new one.

You’ll need a few tools to replace the thermistor on your own. If you haven’t done it before, don’t panic. I’ve replaced a thermistor multiple times and I’ve broken down the process into simple steps. Here are the tools you’ll need to replace the thermistor:

  • A Phillips Head Screwdriver.
  • A ½ Inch Open End Wrench.
  • A bucket for draining water.
  • A Siphon Transfer Pump.
  • Some towels.

When ordering a new thermistor, provide the heater model and serial number to make sure you’re getting the right replacement part. Once you have those things, you can follow these steps to replace a faulty temperature sensor:

Step 01 – Drain The Water Heater

Turn off the power to the water heater. Keep in mind that it’s not safe to work on a unit that has power. Some units can also be connected to more than one branch circuit.

Disconnect all of the branch circuits before you work on the heater. Ideally, you should check the heater with a noncontact ground tester to make sure it’s turned off. Once you’re satisfied, you can move on to drain the water heater.

Open a hot water faucet and keep running the water until it becomes cold.  Then, you can close the inlet valve of the water heater. Keep the hot water faucet open as you do that to relieve the pressure.

Place a bucket under the water heater. Then, remove the outer cover of the heater. The idea behind placing the bucket under it is to catch spilling water. From here on, the steps to drain the heater will vary for a point-of-use model and a two or four-chamber model.

# Point-of-use Units:

Let’s talk about the point-of-use units first. Remove the screws that connect the top plate to the heater. Then, pull the top plate out. Put some towels on top of the water heater to prevent water from getting into the openings.

Then, disconnect the inlet and outlet water lines from the heater. Remove the heating element as well. Put a pump hose inside the water heater’s chamber and then, get the water out through that.

Now that you have drained the water, you can reinstall the heating element and the water inlet and outlet lines. That covers how you can drain the water for the point-of-use models.

# Two And Four-chamber Models:

Now, let’s look at the two and four-chamber models. First, remove the six screws that secure the access plate in its place. Then, remove the access plate and let the water drain into the bucket. The access plate is located at the bottom of the heater in case you’re having trouble finding it.

Once you’re done, you can clean the access plate and the seals. Place the seals properly and reinstall the access plate. Attach the screws that you removed to secure its position. Similarly, repeat the steps for all the access plates. Once you do that, the water will be drained from the water heater.

Step 02 – Replace The Thermistor

You’d have to locate the thermistor that was identified by the error code. It’s important that you replace the right thermistor. Here’s a picture of the thermistor location in the point-of-use models:

thermistor location of state select electric tankless water heater (point-of-use models)

Similarly, you’d have to locate the right thermistor for the two and four-chamber models. In the four-chamber models, there are five thermistors. They are the inlet thermistor, the outlet thermistor, and three intermediary thermistors. You’d have to locate the right one.

In the two chamber models, there are three thermistors. There’s the inlet thermistor, the outlet thermistor, and an intermediary thermistor as well.

Once you’ve located the faulty thermostat, unplug its wire from the control board. Use the ½ inch-open end wrench to turn the thermistor counterclockwise and rotate it. It’ll come loose and you’ll be able to remove it.

Next, install the new thermistor in place of the old one. Use the same wrench and rotate it clockwise to secure it in its place. Ensure that the O-ring is securely in place before you install the new thermistor.

Don’t try to overtighten the thermistor as that can damage it. Once you’ve replaced the thermistor, reconnect the thermistor wire to the control board. 

Step 03 – Return The Heater To Service Mode

Turn on the water supply to the water heater after replacing the thermistor. Open a hot water faucet as well to fill the heater with water. Let it run until the air is completely purged from the heater and the pipes.

If there’s a T&P valve installed, operate it a few times so that any trapped air can escape. Finally, check for leaks. Don’t turn on the water heater if there’s any water dripping.

If you see any leak, seal it first by connecting the heater properly. Then, wait for the heater to dry. You can turn the heater on after that if you’re using a point-of-use model. But there are a few additional things you have to do for two and four-chamber models.

Connect the ribbon cable to the control board. You’ll see two rows of header pins together where you have to connect it. Here’s a picture to help you out:

ribbon cable of state select electric tankless water heater (two and four-chamber models)

Keep in mind that you must connect it correctly as shown in the above picture. If you orient it backwards, the heater will not be damaged but you’ll no longer see the display. So, if there’s no display after you’ve completed the installation, that’s a sign that you’ve messed up.

But there’s no need to panic. Just disconnect the power to the heater and remove the plugs. Rotate it 180 degrees and connect it properly this time. Then, connect the cover of the heater and restore the power of the water heater. That’s all you need to replace the thermistor.


How to prevent the temperature sensor from going bad?

You can extend the lifespan of the temperature sensor by doing regular maintenance of your water heater. Flushing your tank and replacing the anode rod when needed will help in making all heater components last longer.

Should you replace the temperature sensor yourself or hire a qualified technician?

I’ve already shared the steps needed to replace the sensor. If you feel confident that you can do it on your own, you should do it yourself. But if you’re not, you should hire a professional to do the job.

Is it dangerous when the status light blinks?

If the status light flashes once every three seconds, it means the heater is operating normally. You don’t need to do anything there. But if the State Select water heater status light is flashing in other patterns, then it indicates an error code that needs to be fixed.

What is the cost to replace the thermistor?

The thermistor itself isn’t an expensive component. You’d find one in the price range of $10-$15. But you have to spend more on tools if you do the replacement yourself or pay the labor charges if you hire a technician.

Can the water heater work well without the thermistor?

If the heater could work without the thermistor, the manufacturers wouldn’t have made it. Without the thermistor, the thermostat won’t work properly. So, you won’t get water at the right temperature.


Now you know the main reasons behind State Select hot water heater sensor failure and how you can fix this problem. Watch out for the common symptoms. If you notice them, then, you need to do the test and replace the thermistor if needed.

Hopefully, you’ll be able to fix your heater’s problem by following this guide. Well, we also have a dedicated guide on state select water heater leaking water. You can check out it in case you face a water leakage in your water heater.

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