Heat Pump Not Heating in Winter
Quick Answer
If your heat pump isn't heating, first check the thermostat is set to HEAT (not COOL or AUTO). Then check that the outdoor unit is running and not covered in ice. In extreme cold, the auxiliary/emergency heat should activate automatically.
Safe Checks You Can Do
- 1Check thermostat mode - Must be set to HEAT, not COOL or AUTO. Temperature set above room temp.
- 2Check outdoor unit - Is it running? Clear any snow, ice, or debris from around it.
- 3Check both breakers - Heat pumps have separate breakers for indoor and outdoor units.
- 4Try emergency heat - If available, switch to EM HEAT temporarily to stay warm while troubleshooting.
Likely Causes
- Stuck reversing valve
The valve that switches between heating and cooling may be stuck in cooling position.
- Low refrigerant
Insufficient refrigerant reduces heating capacity. Requires professional repair.
- Frozen outdoor unit
Heavy ice buildup prevents heat absorption. Defrost should clear normal frost.
- Outdoor unit not running
Compressor or outdoor fan failure prevents heating. May be electrical issue.
- Extremely cold weather
Below the heat pump's rated capacity, auxiliary heat should kick in automatically.
When to Call a Pro
- Outdoor unit is covered in ice and defrost doesn't help
- System is stuck in cooling mode regardless of settings
- Emergency heat isn't working either
- Outdoor unit makes grinding or screeching sounds
- It's below freezing and you have no backup heat source
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