Noritz Error Code 73: Circuit Board Setting Error
Warning: Your Noritz water heater is experiencing a circuit board setting error, which has caused it to shut down. It's safe to troubleshoot, but don't attempt any repairs yourself.
How to Fix Noritz Code 73
- Step 1: Turn off the power to your Noritz water heater at the circuit breaker.
- Step 2: Wait for 30 seconds, then turn the power back on. The unit should reset and try to boot up.
- Step 3: If the error persists, or you hear unusual noises, call a professional HVAC technician.
How to Reset Noritz Code 73
- Turn off the unit using the power button on the front panel.
- Turn off the gas supply valve.
- Turn off the circuit breaker supplying power to the unit. Wait 30 seconds.
- Restore power at the breaker, then open the gas valve.
- 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 73 Mean?
The Noritz 73 error code indicates a problem with the circuit board's settings. This could be due to a software glitch, a power surge, or a faulty component. The unit has entered a safe mode and shut down to prevent further damage. Before you call a professional, let's try a simple reset.
Common Causes
- A power surge or fluctuation
- Software glitch due to a recent update or power outage
- Faulty component on the circuit board
Diagnostic Steps
| If... | Check | Expected |
|---|---|---|
| The unit powers on but displays the 73 error immediately | Measure the voltage at the circuit board's power supply terminals | 12V DC ±10% (10.8V to 13.2V) |
| The unit doesn't power on at all | Inspect the power cord for any damage or disconnection | Power cord is intact and properly connected |
Applicable Noritz Models
Replacement Parts
| Part | OEM Number | Est. Cost | Where to Buy |
|---|---|---|---|
| Circuit Board | NR-CB-001 | — | Find Part |
Related Codes on Same Models
Other codes that affect the same Noritz model families as 73.
| Code | Description | Severity |
|---|---|---|
| 10 | Flame Failure | Warning |
| 11 | Ignition Failure | Warning |
| 12 | Flame Loss | Warning |
| 14 | Thermal Fuse Failure | Warning |
| 16 | Over-Temperature | Warning |
| 29 | Condensate Drain Issue | Warning |
| 31 | Inlet Thermistor Failure | Warning |
| 32 | Outlet Thermistor Failure | Warning |
| 33 | Heat Exchanger Thermistor Failure | Warning |
| 43 | Water Level/Neutralizer Issue | Warning |