State tankless water heater displays E13; water temperature may be unstable.

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 recirculation thermistor, Loose sensor wiring, Incorrect sensor placement on return line

Safety: Turn off power before working on wiring.

Locate recirc sensor: On models with built-in recirculation, find the sensor on the recirculation return line.
Inspect and reseat: Check that the sensor is firmly attached to the pipe and that the wiring connector is secure.
Test sensor: Measure resistance and compare to the State thermistor chart. Replace if out of range.
Verify plumbing: Ensure the recirculation return is connected to the correct port per the installation manual.

Medium 3/5

Recirculation Temperature Sensor

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