H1
Day & Night
Outdoor Temperature Sensor Fault (Heat Pump)
H1 code, heat pump may run in backup heat only, poor heating performance
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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
Failed outdoor ambient temperature sensor, Sensor not mounted in free air, Damaged sensor wiring, Faulty outdoor control board sensor input
How to Fix / Troubleshooting
Safety first: Turn OFF power at the outdoor disconnect before accessing the sensor.
- Step 1 – Locate ambient sensor: On Day & Night heat pumps, the outdoor ambient sensor is usually mounted near the coil inlet or on the control panel, exposed to outdoor air.
- Step 2 – Check mounting: Ensure the sensor is not touching hot surfaces or enclosed inside the cabinet where it cannot sense true outdoor temperature.
- Step 3 – Inspect wiring: Verify the sensor wires are intact and the connector at the board is secure.
- Step 4 – Test sensor: With power OFF, measure resistance and compare to the temperature chart. Replace if out of range.
- Step 5 – Restore power: After replacement, clear codes by cycling power and test heating operation.
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Repair Difficulty
Medium
3/5
Required Part
Outdoor Ambient Temperature Sensor
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