What steps should I take if my Ruud Ultra Plug-in Heat Pump with HydroBoost (120V Shared Circuit) presents Alarm Code A103?

CAUTION: For your safety, DO NOT attempt repair of electrical wiring, controls, heating elements, or other safety devices. Refer repairs to qualified service personnel.

Possible Cause: Lower tank temperature sensor malfunction, leading to the heater being disabled. What To Do:

1. Review and ensure the connections of the wiring and sensors are secure.
2. If you’re equipped with a multimeter, measure the Ohm reading on the thermistors. Always reference the Ohm chart to interpret readings based on the ambient temperature.
3. Through the device’s interface, proceed to Service –> Sensors. A reading of -40°F signifies the circuit is open, while a reading of +250°F indicates a short in the circuit. For an accurate diagnosis, switch off the unit, detach the thermistor from its board, and then re-assess the Ohm reading.

This answer is applicable for the following model: Ruud Ultra Plug-in Heat Pump with HydroBoost (120V Shared Circuit).