Noritz error code 90

Whether you’re a homeowner, a professional installer, or someone researching water heaters, encountering the dreaded noritz error code 90 can be quite perplexing. This error signifies a common but crucial issue: bad combustion. But fear not! In this article, we will delve deep into the intricacies of this error, its potential causes, and most importantly, how you can troubleshoot and rectify it.

Primary Causes of the Error

There are several factors that can trigger the Noritz error code 90. Understanding these causes is the first step in the troubleshooting journey:

  1. Gas-Related Problems: When the heater fails to reach the desired temperature, the problem often lies with the gas supply. Insufficient inlet gas pressure or obstructions in the manifold can impede the heater’s performance.
  2. Bypass Issues: If there’s a disparity between the outlet and heat exchanger temperatures, it might point to an overly open bypass. This component may need checking or replacement.
  3. Air or Venting Troubles: If all temperatures are consistent but the fan speed correction is high, then the issue might be due to venting problems or air blockages.
Noritz error code 90

How to fix Noritz error code 90?

When confronted with the Noritz error code 90, one of the primary culprits is often related to gas inconsistencies. Ensuring that the heater has an adequate gas supply is essential for optimal performance. First and foremost, it’s imperative to check the inlet gas pressure. This pressure plays a critical role in ensuring that the water heater burns fuel efficiently. It should never dip below 5”H2O during maximum operation. If the pressure is consistently low, it could be a sign that there’s an issue with your home’s gas supply or the heater’s inlet.

Another vital area to inspect is the manifold and burner. These components should be free from obstructions that might hinder gas flow. Over time, debris can accumulate, causing inefficiencies. A simple yet effective way to clean the manifold orifices is using a paperclip. For the burner, a burst of compressed air can effectively remove any accumulated debris, ensuring clean and efficient combustion. By addressing these gas-related concerns, your Noritz water heater should function seamlessly, providing you with consistent hot water.

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Fix 2: Ensuring Efficient Airflow and Venting in Noritz Water Heaters

A crucial factor in the proper functioning of any water heater is the efficiency of airflow and venting. When the Noritz error code 90 surfaces, it may hint at complications in these areas. Venting, in particular, plays an instrumental role in ensuring the water heater’s safe and efficient operation. A primary step in rectifying this is to examine the venting system. The length of the vents, as well as the number of bends or elbows, can drastically affect performance. It’s essential to refer to the installation manual and confirm that your venting setup adheres to Noritz’s guidelines.

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Blockages in the venting can also be a significant concern. Elements like snow, bird nests, or even ice can obstruct vents, causing inefficient combustion. Regularly inspecting and clearing these vents can prevent such issues. Furthermore, dampers need to be in optimal condition. Any damage, or even minor obstructions like screws, can affect their operation, impeding airflow. Ensuring that these components are clean and undamaged can resolve many issues associated with the Noritz error code 90, restoring your water heater to its prime state.

Fix 3: Checking and Adjusting Bypass Components in Noritz Water Heaters

An often overlooked but essential component in the water heating system is the bypass mechanism. For those encountering the Noritz error code 90, there might be issues related to the bypass that need attention. The bypass ensures that the water heater delivers a consistent temperature, and if it’s not functioning correctly, temperature discrepancies can arise.

To start with, it’s crucial to observe the heat exchanger temperature. If the heat exchanger reads within the 140F-180F range, but the outlet temperature fails to match the set target, the bypass might be the issue. An overly open bypass can reduce the unit’s efficiency, leading to inconsistent heating.

In such cases, it might be necessary to adjust or even replace the bypass. But, before taking this step, it’s always advisable to consult the user manual or a professional to understand the nuances of your specific Noritz model. Addressing bypass-related issues can not only resolve the error code 90 but also enhance the overall performance and longevity of your Noritz water heater.

Fix 4: Configuring Dipswitches and High-Elevation Settings in Noritz Water Heaters

The modern intricacies of water heaters often revolve around digital configurations, and Noritz models are no exception. When deciphering the cause behind the Noritz error code 90, adjusting the dipswitches and high-elevation settings can often be the solution.

Dipswitches, small switches on the unit’s circuit board, play a pivotal role in determining the operational parameters of the water heater. If these switches are not correctly set, it can disrupt the unit’s combustion balance, leading to inefficient performance. Make sure to consult the installation manual to ensure that the dipswitches align with the manufacturer’s recommendations for your specific installation environment and conditions.

Additionally, for those residing in high-altitude areas, the water heater’s settings need adjustments to account for the reduced air density. The high-elevation settings ensure the heater compensates for these conditions, maintaining optimal combustion. Incorrect settings can lead to improper burning, contributing to the error code 90.

By regularly inspecting and adjusting the dipswitches and high-elevation settings, homeowners can ensure their Noritz water heater operates seamlessly, delivering warm water with utmost efficiency.

Fix 5: Periodic Maintenance and Cleaning of Noritz Water Heaters

Maintaining the pristine condition of any device is essential, and Noritz water heaters are no different. Over time, contaminants and foreign elements can compromise the efficiency of the heater, leading to the Noritz error code 90.

A common area of concern is the fan of the unit. Positioned to aid in the combustion process, this fan can attract dirt and debris, especially if located near places like laundry rooms or kitchens. Dust from outside, lint from fabrics, or even grease particles can accumulate on the fan, making it work harder than necessary. This can lead to inefficient combustion. Regularly cleaning the fan, ensuring it’s free from dust and grime, can help in restoring the heater’s efficiency.

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Another critical aspect is checking for external blockages or obstructions. Over time, the external parts of the unit, like the venting system, can be obstructed by foreign materials. Regularly inspect the exterior for signs of blockages such as fallen leaves, insect nests, or other debris.

Lastly, investing in a routine professional inspection can be a game-changer. Experts can identify minor issues before they escalate, ensuring your heater runs smoothly. By incorporating regular maintenance and cleaning practices, you can not only address the error code 90 but also extend the lifespan and performance of your Noritz water heater.

Fix 6: Assessing and Rectifying Electrical Components in Noritz Water Heaters

The intricacies of water heaters, like the Noritz models, often stretch beyond just combustion and flow. At the heart of their operations lie intricate electrical components that ensure the heater functions seamlessly. Encountering the Noritz error code 90 could sometimes point towards these electrical aspects needing attention.

One of the first things to check is the electrical connections within the unit. Loose or corroded connections can disrupt the heater’s performance. Ensure that all wires are securely connected, and there’s no sign of wear or damage. If any wires appear frayed or corroded, they should be replaced immediately to prevent further complications.

Another crucial area is the circuit board. This board orchestrates the overall functioning of the heater. Over time, due to moisture or wear, it can develop issues. Look out for any visible damages or burnt spots on the circuit board, which could indicate a malfunction. In cases where the circuit board appears compromised, it’s recommended to consult a professional or consider a replacement.

Finally, the sensors integrated into the heater play a pivotal role in monitoring various parameters, like temperature and flow. A malfunctioning sensor can provide incorrect readings, leading to inefficient operations. Regularly inspecting and, if necessary, replacing faulty sensors can rectify many issues linked to the Noritz error code 90.

By paying close attention to the electrical components and ensuring they function optimally, homeowners can significantly enhance the efficiency and reliability of their Noritz water heater.

Fix 7: Ensuring Proper Water Flow and Pressure in Noritz Water Heaters

Water flow and pressure are foundational to the efficiency of a water heater. In the case of the Noritz models, an imbalance in these factors can trigger the notorious error code 90. A system’s inability to maintain consistent flow rates can lead to abrupt temperature changes and inefficient combustion.

To begin with, it’s imperative to check the system’s water filters. Over time, sediment and mineral build-ups can clog these filters, obstructing the smooth flow of water. Cleaning or replacing clogged filters can immediately enhance the heater’s performance.

Next, consider inspecting the main water supply. If the pressure is inconsistent or too low, it can affect the heater’s ability to function correctly. Installing a water pressure regulator or adjusting the existing one can help maintain the optimal pressure required by the Noritz unit.

Lastly, the internal valves and flow sensors of the heater need attention. These components dictate the water’s movement and detect any anomalies in the flow. If they malfunction or get clogged, the heater might fail to deliver consistent temperatures. Periodic inspections and cleaning of these components can prevent such hiccups.

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By emphasizing consistent water flow and pressure, homeowners can ensure their Noritz water heater functions efficiently, providing a steady supply of warm water without the inconvenience of error codes.

Fix 8: Monitoring Ambient Environmental Conditions for Noritz Water Heaters

The environment surrounding a water heater can often be an overlooked aspect, but it plays a crucial role in the unit’s performance. Environmental factors, both external and internal, can affect the heater’s operations, leading to issues like the error code 90.

Externally, it’s essential to ensure that the heater is not exposed to extreme cold. Freezing temperatures can cause internal components to malfunction or even freeze, affecting the heater’s efficiency. Installing the heater in a protected space or using insulation can mitigate such risks.

Internally, the ambient oxygen levels are crucial for efficient combustion. Ensure that the room housing the water heater has ample ventilation. If the oxygen levels drop, it can lead to incomplete combustion, prompting error codes.

Additionally, ensure that the heater isn’t exposed to chemical fumes or corrosive atmospheres. Such environments can damage the internal components over time. It’s advisable to keep heaters away from areas where chemicals are stored or used frequently.

By being vigilant about the ambient environmental conditions and ensuring that the Noritz water heater operates in a safe and stable environment, homeowners can prolong the unit’s life and keep it free from persistent error codes.


The Noritz error code 90, while common, is a clear indicator that your water heater needs attention. By understanding its causes and knowing how to diagnose it, you’re already halfway to a solution. Remember, safety first! If you’re uncertain about any step, consulting a professional is always the best course of action. Regular maintenance and periodic checks can also prevent such errors, ensuring efficient heating for your home.


What is the Noritz error code 90?

It’s a code indicating bad combustion in Noritz water heaters.

How often should I inspect my Noritz heater?

Regular checks every six months can help prevent issues.

Can clogged filters cause error code 90?

Yes, sediment build-up can obstruct water flow, leading to errors.

Is the error related to electrical issues?

Sometimes. Faulty electrical components can trigger the error.