Noritz Error Code 90: How To Fix [2023]

Nortiz Tankless heating systems, with their ingenious error detection systems, are leaps and bounds above their competitors. But what does Error code 90 herald on these devices? Let's find out!

I have had a Nortiz NRC series heater for quite some time now, and I have become accustomed to their nifty little issues.

And so, on an unfortunate Sunday morning, when the error code 90 popped up, I knew just what I needed to do to get it fixed.

To fix error code 90 on Nortiz, first, run a Maintenance Monitor test on the Heater. If the water temperature or the fan speed is not up to the mark, you may have to service the associated elements like the internal filter, the flash rods, the fan, or the intake manifolds.

Read on for a more detailed account of how to fix a Nortiz Heater showing error code 90.

Run a Maintenance Monitor Test on Nortiz

Maintenance Monitor Test on Nortiz

Before getting on with the troubleshooting, you have to know what code 90 means on Nortiz.

Error code 90 on Nortiz indicates an issue with the heating/combustion. Reasons could be temperature disparity, fan motor issues, clogged-up intake/outlet valves, or ill-configured DIP switches.

On new installations, code 90 can arise as a result of insufficient gas pressure.

In older units, the error code arises due to impurities piling up on the internals. Carrying out Routine maintenance should do the trick.

To ascertain the exact culprit of the issue, the first thing to carry out is a Maintenance Monitor test.

With Maintenance Monitor Modes on Nortiz, you get to know the status of the various parameters on your Nortiz.

Here's how to do so:

1. First, set the Temperature to the desired level. 120F is the preferred limit.

2. Open up the water and gas intake to their maximum limit. Ensure the front cover is on.

3. With the unit powered ON or OFF, press the mode button on the Display window for about 2 seconds.

Display window Nortiz

You can also access Monitoring modes from the Remote Control by pressing and holding the Up and Down buttons simultaneously for 2 seconds.

4. Ensure that the device is now powered ON and running.

5. Wait till a number like '03' pops up.

6. You can cycle through the various Monitoring modes using the Up and Down buttons.

With Monitoring Modes accessed on your Nortiz, here are the most crucial parameters pertaining to error code 90 to check for:

Monitor ModeIndicationIdeal ConditionUndesirable condition
31Outlet Water TemperatureSet Temperature (+ or - 2 units also acceptable)Below the set limit
32Heat Exchanger TemperatureSet Temperature (can exceed the limit a little)Higher than the limit
49Fan speed Correction100%Exceeds 100%
Maintenance Monitor Modes pertaining to Error code 90

Water Temperature Disparities

As noted above, the prime reason error code 90 appears on Nortiz is due to combustion-based issues.

And the Maintenance Monitoring modes indicative of such issues are MM#31 and MM#32.

MM#32 may not be available in entry-level Nortiz appliances since they lack a bypass apparatus.

And so, if either of these parameters seems to vary, you can affirm the chances of the issues with combustion.

Under normal circumstances, MM#31, which indicates the temperature of the outlet water supply, will climb its way up to the set temperature.

Ideally, this indicator should match the set temperature with a leeway of about 2 degrees.

If MM#31 indicates a temperature well below the set temperature, the internal combustion unit may have issues heating the water to the desired temp.

Probable causes of such an incident are low gas pressure, clogged intake orifices, or undesirable external conditions.

The MM#32 mode also corresponds to this variation by showing a drastically different value.

But if the MM#32 mode seems steady but MM#31 shows an undesirable value, the bypass unit may be opened too much.

Checking the bypass unit and replacing it if it's damaged would be an ideal fix.

Either way, some of the troubleshooting steps that might yield results in this case are:

  1. Clean the Manifold orifices.
  2. Clean the internal filters.
  3. Increase the Gas intake.
  4. Consult an expert about the same.

On the other hand, if both these modes seem unperturbed and are doing just fine, check MM#49 next:

Check the Fan Speed Mode

Another parameter that indicates the optimal working of Nortiz combustion is the fan speed correction mode.

As indicated by MM#49, the fan should always be 100% with the front cover on and regardless of the operating mode.

If and when the device fails to receive the optimal amount of air or if there is an issue with the exhaust, the fan starts to throttle to compensate for the inconsistencies.

Although this compensation may seem an ideal adjustment for the losses, it is an abnormal scenario and can damage the device.

Thus, the device puts up the error code 90.

Recommended fixes in this case are:

  1. Check and ensure optimal air intake.
  2. Clean the Fan.
  3. Check and configure the DIP switches for elevation.
  4. Check and clean out blockages in the vent.

With that said, let's get on with the troubleshooting:

Check and Clean Various Elements of Nortiz

Dirty Intake filters and debris-infested Fans are the most common causes for error code 90 on Nortiz.

Clogged-up Fire Rods can also inhibit combustion and limit the water temperature from attaining the set limit.

A simple fix to clear up such inconsistencies is to perform routine maintenance on Nortiz.

Let's start with the exterior stuff first:

Check and Clean the Intake Filters

Nortiz comprises various intake manifolds to regulate the supply of air intake, gas intake, and water intake.

And they all come with specialized filters to keep debris and other undesirable elements from entering the device.

Over time, these filters will get clogged and dirty.

Fortunately, though, they are easy to be cleaned.

Here's how to do so:

1. First, check for rust and other signs of corrosion on the device exterior, including the intake valves. Make sure they do not leak.

2. Remove the conversion kit from the intake, if you have one, and check for dust and debris inside.

conversion kit

3. Pluck out the filter screen and clean it with running water. Brush off dust and debris. Dry it thoroughly before reinstalling.

4. Now, close the Water Inlet valve by turning the lever to the right.

5. Unscrew the inlet and outlet drain caps to release retaining water. Open a couple of hot water fixtures in your premise to release the pressure.

inlet and outlet drain caps

6. Unscrew the Water drain valve filter and clean it thoroughly. Dry it up before reinstalling.

Water drain valve filter

7. Screw back on the drain caps and turn ON the water inlet valve.

8. Check for leaks.

Next, let's check and clean the interior elements:

Check and Clean the Interior Elements

The components to take a look at here are the Fire Rods and the Fan module.

Residue buildup on Fire rods is not a good sign, and the same goes for debris on the Fan motor. With time, they can affect the optimal working of the device.

And so, it's best to check and clean these components before things take a turn for the worse.

Here's how to do so:

1. Unplug the device from the power source and turn OFF the gas valve.

2. Remove the front cover by unscrewing the screws using a Phillips head screwdriver.

3. Detach the white connectors attached to the Fire Rods and Ignition plugs.

Fire Rod unit

4. Unscrew the screws securing the Fire Rod and Sensor module.

Take caution while removing the Fire Rod module since the gasket protecting the module is very delicate. Avoid using power tools.

5. Carefully clean the Fire Rod and the Ignition Plug with fine-grit sandpaper or similar material with a gritty texture. Do not touch the probe end. Make sure it's free of any residue.

How To Access the FAN Module

Here's how to access the Fan module:

1. Unplug the Gas Manifold connection by pressing the top of the connector.

Gas Manifold connection

2. Remove the C-clamp securing the Gas Manifold by gripping the manifold Pipe and pulling out the clamp.

3. Unseat the Gas Manifold by removing the four screws using a Phillps head screwdriver.

Gas Manifold

4. Push up the Gas Manifold Pipe to fully remove the Gas manifold.

5. Remove the GFCI mounting plate by unscrewing the two screws.

GFCI mounting plate

6. Disconnect the Fan connector.

Fan connector

7. Unscrew the Fan Module from the device.

8. Carefully brush off residue, dust, and debris from the Fan blade. Use can also use compressed air to do so.

Reinstall all the components carefully and check for the issue now.

Configure the DIP switches

Another grey area that can trigger error code 90 is improperly set DIP switches.

DIP switches determine how the device operates for a given scenario, say higher elevation or longer pipe lengths.

And as so it happens, the two most important parameters that pertain to error code 90 are the elevation at which the device is installed and the pipe length.

But first, you'll have to access the DIP switches on Nortiz.

Nortiz water heaters come with 8 DIP switches numbered 1 to 8.

Here's how to access them:

1. Unplug the power supply from Nortiz.

2. Unscrew the front cover.

3. Locate the DIP switches on top of the Circuit Board.

DIP switches on Nortiz

If you have installed the device on the outside, switch on DIP switch #2. To accommodate the SV conversion kit, turn ON DIP switch #3.

Now, depending on the scenario, here are the various configs you need to implement:

For Elevation Adjustments

DIP switches #5 and #6 are the ones to change.

ElevationDIP switch #5DIP switch #6
0 - 2000 ftOFFOFF
2001 - 4000 ftONOFF
4001 - 7000 ftOFFON
7001 - 10000 ftONON
DIP switch configs for elevation

For Pipe Length Adjustments

DIP switches #7 and #8 should be changed in this regard.

Pipe/Vent length ConditionDIP switch #7DIP switch #8
<33 ft with 2-inch pipeOFFOFF
>=33 ft with 2-inch pipeONOFF
<75 ft with 3-inch pipeOFFON
>=75 ft with 3 -inch pipeONON
DIP switch config for pipe length

Final Thoughts

And there you have it, a comprehensive guide to troubleshooting error code 90 on Nortiz.

With gas-related issues, get in touch with a certified professional to take a look. It's best not to tinker with such tasks for yourself.

If things don't seem to get well even after going through with the suggested tips, contact the customer services of Nortiz for further assistance.

Worn-out and rusted parts should be replaced. Do not try to salvage them.

Frequently Asked Questions (FAQ)

How do I reset my Noritz tankless Heater?

Nortiz devices do not come with a reset button. To reset Nortiz, unplug the power supply for about 30 seconds and plug back in the cable.

Why does my Noritz water heater keeps shutting off?

Nortiz heaters keep shutting due to power-related issues or insufficient water supply. Check and make sure sufficient electricity is being supplied to the device. Check the water inlet pressure and make sure the inlet filter isn't clogged.

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About Doug Stevenson

Hey! I'm Doug, My passion for tech started by fixing phones and computers for my friends and family.

I started Blinqblinq to give reliable tech advice to anyone who needs it, for free! If you have questions on anything tech-related, feel free to contact me.

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Doug Stevenson

Hey! I'm Doug, My passion for tech started by fixing phones and computers for my friends and family.

I started Blinqblinq to give reliable tech advice to anyone who needs it, for free! If you have questions on anything tech-related, feel free to contact me.

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