Rheem tankless water heater displays E40 and shuts down

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

Faulty fan speed sensor, Loose fan connector, Obstructed fan wheel, Control board not reading tach signal

Safety first: Turn OFF power and gas.

Inspect fan: Remove front cover and check the combustion blower for debris or damage.
Check connector: Ensure the multi-pin fan connector is fully seated and free of corrosion.
Spin test: With power OFF, spin the fan by hand to confirm it moves freely.
Replace fan assembly: If the tach sensor is integrated and faulty, replace the entire combustion blower assembly.

Hard 4/5

Combustion Blower Motor

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