Heat PumpTroubleshooting2026-01-10
Heat Pump Not Heating: Causes and Fixes
A heat pump that won't heat can be a thermostat mode, dirty coils, low refrigerant or a defrost issue.
A heat pump not heating well has several possible causes, from simple settings to refrigerant faults. Here's how to narrow it down.
Simple checks first
Confirm the thermostat is in HEAT (not EMERGENCY/AUX or COOL), check and replace a dirty filter, and make sure the outdoor unit is clear of snow, leaves and debris.
Deeper causes
Frozen outdoor coils, low refrigerant from a leak, a failing reversing valve, or a defrost-control fault all reduce heating. These need a technician with refrigerant certification.
Key takeaways
- Set the thermostat to HEAT, not AUX-only
- Clear snow and debris from the outdoor unit
- Replace dirty filters
- Low refrigerant means a leak — needs certified repair
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Frequently asked questions
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