Reliance hybrid water heater shows F5 and may stop heating in heat pump mode

Safety first: Turn OFF power. Avoid relocating sensors away from their designed positions.

Steps to check:

• 1. Locate ambient sensor: Find the sensor near the air intake or on the top shroud where it measures room air temperature.
• 2. Ensure free airflow: Make sure the sensor is not buried in insulation or touching hot components. It should be exposed to room air.
• 3. Inspect wiring: Check the harness for cuts or pinches and reseat the connector at the control board.
• 4. Measure resistance: Disconnect and test the sensor with a multimeter. Compare to the thermistor chart. Replace if out of spec.
• 5. Re-test unit: After replacing or reseating the sensor, restore power and verify that F5 clears and heat pump operation resumes.

Note: Extremely low or high ambient temperatures may also limit heat pump operation even with a good sensor.