65
Richmond
Water Flow Control Valve / Bypass Valve Fault
Richmond tankless heater displays error 65; unit may start then shut down quickly.
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Safety Warning
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.
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Possible Causes
Stuck modulating water valve, Scale buildup in water control valve, Failed water valve motor, Loose valve wiring
How to Fix / Troubleshooting
Safety first: Turn OFF power and close the water supply valves. Relieve pressure by opening a hot water tap.
- Locate water control valve: Inside the unit, find the motorized water control or bypass valve on the cold water side.
- Inspect wiring: Check the valve motor connector and harness for damage or loose connections. Reseat the plug.
- Descale system: Perform a full descaling of the heat exchanger and internal water passages. Scale can cause the valve to stick.
- Manual movement (if accessible): Some valves allow gentle manual rotation of the shaft to free it. Do not force; refer to the service manual.
- Replace valve if needed: If error 65 persists, the water control valve assembly or its motor is likely defective and should be replaced.
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Repair Difficulty
Hard
4/5
Required Part
Water Control Valve
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