Noritz Error Code 66: Bypass Flow Control Valve Failure
Warning: Your Noritz water heater is locked out due to a potential safety issue. Do not attempt to fix it yourself.
How to Fix Noritz Code 66
- Step 1: Turn off the power to your water heater at the circuit breaker.
- Step 2: Contact a licensed HVAC technician to diagnose and repair the issue.
- Step 3: Do not attempt to open the water heater or tamper with any internal components.
How to Reset Noritz Code 66
- 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 66 Mean?
Error code 66 on your Noritz water heater indicates a failure in the bypass flow control valve. This valve is responsible for regulating water flow through the heat exchanger. If it fails, it can cause the water heater to overheat, posing a safety risk. The water heater will shut down to prevent any potential hazards.
Common Causes
- Wear and tear on the bypass flow control valve
- Mineral buildup or debris blocking the valve
- Incorrect water pressure
- Faulty valve due to manufacturing defect
Diagnostic Steps
| If... | Check | Expected |
|---|---|---|
| Water heater is not producing hot water | Check the bypass flow control valve for any visible damage or blockages | Valve should be clean and undamaged |
| Water pressure is above 150 PSI | Check the water pressure regulator | Water pressure should be within the recommended range (typically 50-80 PSI) |
Applicable Noritz Models
Replacement Parts
| Part | OEM Number | Est. Cost | Where to Buy |
|---|---|---|---|
| Bypass Flow Control Valve | NOR-123456 | — | Find Part |
Related Codes on Same Models
Other codes that affect the same Noritz model families as 66.
| 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 |