H2
American Standard
Low Outdoor Temperature / Protection Mode
Heat pump shows H2 and alternates between heating and standby frequently
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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
Outdoor ambient below operating range, Faulty outdoor ambient sensor, Incorrect thermostat balance point settings, Defective American Standard heat pump control logic
How to Fix / Troubleshooting
Safety first: No internal panels need to be opened for basic checks.
- Check outdoor temperature: Verify that the outdoor temperature is within the operating range specified in the American Standard manual. Extremely low temperatures may limit heat pump operation.
- Verify thermostat settings: Ensure the thermostat is configured with appropriate auxiliary heat balance points so the system can switch to backup heat when needed.
- Inspect outdoor ambient sensor: If accessible, check that the sensor is not damaged and is mounted in free air away from direct sunlight or exhaust.
- Professional evaluation: If H2 appears in moderate weather, a technician should test the ambient sensor and control board.
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Repair Difficulty
Medium
3/5
Required Part
Outdoor Ambient Temperature Sensor
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