Noritz Tankless Water Heater No Display [4 Easy Solutions]

Your Noritz tankless water heater remote display is blank and surprisingly there isn’t any error code seen. It can happen for many reasons but the common causes are incorrect power voltage, defective water flow sensor, bad thermistor, and faulty heat exchanger. 

As we’ll break down all these common reasons, why they happen, and their easy solutions, read to troubleshoot your Noritz tankless water heater no display problem ASAP.

Noritz Tankless Water Heater No Display [Easy Solutions]

There are a few things that could be causing you this issue where you get an empty display and your unit doesn’t work properly. Now we’ll take a look at the common causes and the simple solution for individual causes here.

1. Incorrect Power Voltage

A high or low voltage supply to your unit can make it stop working properly.


The first thing you need to do is to check the voltage your unit needs and what voltage it is getting. If the voltage is too low, your unit won’t run properly. But, if you have a high-voltage supply, your unit’s fuse is probably tripped. This is the reason you aren’t getting a display even when the unit is powered.

Check the fuse and fix it or replace it if it’s blown. Take a look at your unit’s wiring as well. Make sure all connections are tight and in their place.

2. Defective Water Flow Sensor

A water flow sensor can detect the water flow and turns on your water heater to start heating water immediately. It can also detect the rate of flow of water. 

So, If there is anything wrong with your water flow sensor, your heater will not get the signal to turn on. You can test whether this is the cause of your problem by checking if the fan is working when the hot water valve is open. 


The water flow sensor may need to be replaced to get your heater working. Here’s how you can replace your water flow sensor:

Step 1: Turn off the heater water, power, and gas supply. Remove the heater cover and the four screws you see. 

Step 2: After removing the filter, drain the remaining water in the unit.

Step 3: Locate the flow sensor in your unit. It is likely to be located above the cold water connection. Your unit may have two sensors. 

Step 4: There are two “C” clamps that you need to remove. 

Step 5: You can spot a pipe in front of the flow sensor. Pull it out. Pull up the flow sensor from the bottom of the heater. If you see any water draining out, dry it with a paper towel to keep the wire connections dry.

Step 6: Inside the short end of the flow sensor, there is a plastic dome.  After placing the long end of the flow sensor in your palm and holding the top with the fingertips of the same hand, Push down on the dome with a screwdriver. 

Step 7: A silver ring and the flow sensor cylinder will come out. Now, swap the new flow sensor with the old one by reversing all the steps you’ve performed so far.

3. Bad Thermistor

The thermistor is a resistor used in your water heater that adjusts to changes in temperature. If your thermistor is malfunctioning, the entire circuit of your heater will stop working properly. 


Test your thermistor to see if it working properly. If not, you’ll need to replace it. You’ll need a soldering iron and a multimeter to conduct this test. Here’s how to test a thermistor:

Step 1: Turn on the resistance mode of your multimeter.

Step 2: Put the two terminals of the multimeter up against the two leads that are on the thermistor. 

Step 3: Now, you’ll need to heat the soldering iron and after it is heated, use the soldering iron to heat the thermistor as well. Move the tip of your soldering iron to the thermistor.

Step 4: Keep note of the multimeter heating as you are heating the thermistor.

Step 5: With the increase in temperature of the thermistor, the reading should also steadily get higher if the thermistor is a positive temperature coefficient thermistor. 

Step 6: If you have a  negative temperature coefficient thermistor, its reading should steadily decline as you supply more heat to it.

Step 7: If your multimeter reading is zero, infinity, or unchanged, then your thermistor is bad. If the change of reading isn’t steady and gradual, that too is a sign of a faulty thermistor.

4. Faulty Heat Exchanger

The heat exchanger in your water heater is a device that allows the exchange of heat between two fluids without them mixing or coming into direct contact.

If your heat exchanger leaks, your water heater will not function properly. You’ll get incorrect outlet water temperatures.


If you are getting incorrect outlet water temperatures, you should check your heater exchanger for leaks. Leave this task to a professional as this can be quite complex. If the test show’s a leak, you need to replace the heat exchanger in your water heater with a new one. But, remember, replacing the heat exchanger is a little bit risky and costly. In that case, it’s wise to replace the whole water heater system.


Do Noritz tankless water heaters have a pilot light?

Ans: No, they don’t have a pilot light. They come with an automatic ignition device.

What does code 11 mean on a Noritz tankless water heater?

Ans: Code 11 on a Noritz tankless water heater means that the unit isn’t fighting up to heat the water. This issue can be caused by-

  • Insufficient gas supply
  • Debris in the ignition plug
  • Insufficient airflow

What does it mean when a tankless water heater beeps?

Ans: Typically, tankless water heaters beep and display an error code at the same time. This is to notify you that something is wrong with your water heater’s system. Each water heater error code indicates a specific issue. Read the manual to know the meaning. 

Should I turn off the tankless water heater if the water is off?

Ans: You don’t need to turn it off as in the case of a tankless water heater, heating elements are only running when you call for water. There is no waste of energy by constantly running heating elements. So, you can keep it on. 

How often should I flush my tankless water heater?

Ans: Flushing once a year is good for both tankless units and units that come with a tank. 


We wouldn’t recommend you try performing the solutions that we provide for troubleshooting Noritz tankless water heater no display on your own if you don’t have any experience with fixing home appliances.

But experienced or not, hopefully, now you have a good idea of what needs to be done to fix the issue. If you have more queries, comment below and we’ll do 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.

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