Noritz Error Code 33: Heat Exchanger Thermistor Failure

Severity
Warning
Type
digital display
Where to look
front panel
Estimated repair cost: $500 — $1500 (parts + labor)
Warning: Your Noritz water heater is locked out due to a heat exchanger thermistor failure. It's safe to operate, but needs professional repair.

How to Fix Noritz Code 33

  1. Check if the water heater is still under warranty. If so, contact Noritz for repair or replacement.
  2. Turn off the power to the water heater at the circuit breaker for safety.
  3. Contact a licensed HVAC technician for repair. Do not attempt to fix this issue yourself.

How to Reset Noritz Code 33

  1. Turn off the unit using the power button on the front panel.
  2. Turn off the gas supply valve.
  3. Turn off the circuit breaker supplying power to the unit. Wait 30 seconds.
  4. Restore power at the breaker, then open the gas valve.
  5. Turn the unit back on. If the error returns, the underlying issue needs repair.

Resetting clears the code from the display but does not fix the underlying fault. If the code returns after reset, proceed to the diagnostic steps above.

What Does Noritz Error Code 33 Mean?

The error code 33 on your Noritz water heater indicates a failure in the heat exchanger thermistor. This component measures the temperature of the heat exchanger and sends this information to the control board. When it fails, the system locks out to prevent overheating and potential damage. This is a common issue in Noritz water heaters and is typically caused by normal wear and tear or exposure to hard water.

Common Causes

  • Wear and tear over time
  • Exposure to hard water
  • Manufacturing defect
  • Electrical short or open circuit

Diagnostic Steps

If... Check Expected
The water heater is displaying error code 33 Measure the resistance of the heat exchanger thermistor using a multimeter. It should be between 1000 to 2000 ohms at room temperature. A reading outside this range indicates a failed thermistor.
The thermistor resistance is within the expected range Inspect the wiring and connections to the thermistor for any signs of damage or corrosion. No damage or corrosion should be present.

Applicable Noritz Models

Replacement Parts

Part OEM Number Est. Cost Where to Buy
Heat Exchanger Thermistor NOR-30066 — Find Part

Related Codes on Same Models

Other codes that affect the same Noritz model families as 33.

Code Description Severity
10 Flame Failure Warning
11 Ignition Failure Warning
14 Thermal Fuse Failure Warning
29 Condensate Drain Issue Warning
31 Inlet Thermistor Failure Warning
32 Outlet Thermistor Failure Warning
43 Water Level/Neutralizer Issue Warning
45 Water Leak Detected Warning
51 Fan Motor Failure Warning
61 Fan Motor Failure Warning