Noritz Bypass Flow Control Valve Fault

Error code 66 appears; unit may not modulate water flow correctly.

This repair may involve working with high voltage components or water connections. Always unplug the appliance before removing any panels.

If you are not confident in your ability to perform this repair safely, we strongly recommend contacting a professional technician.

Possible Causes

Failed bypass valve motor, Debris obstructing bypass passages, Wiring harness fault, PCB control failure

Safety first: Turn OFF power and gas. Close water valves before disassembly.

Steps to check and correct:

Flush system: Sediment can jam the bypass valve. Perform a descaling flush and ensure clean water supply.
Inspect wiring: Check the bypass valve motor connector and wiring for damage.
Reset and test: Restore power and run hot water. If error 66 persists, the bypass valve assembly or PCB must be replaced by a qualified technician.

Hard 4/5

Bypass Valve Assembly

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