What's normal
- Air that feels lukewarm. Heat pump air is warm, not hot like a gas furnace. It's normal for it to feel cooler at the vent.
- Defrost cycles. In cold, damp weather, frost builds on the outdoor coil. The unit periodically reverses for a few minutes to melt it, sometimes with a whoosh and some steam.
- Backup heat on very cold nights. Electric heat strips help out when it's near freezing.
What isn't normal
- The outdoor unit is encased in ice that doesn't clear after defrost
- The system is stuck on auxiliary or emergency heat
- The outdoor fan isn't spinning, or the unit is blowing cold air in heat mode
- Winter electric bills spike dramatically
- The system works in cooling mode but not heating (often a reversing valve or control issue)
Common causes
Failed defrost controls or sensors, low refrigerant, a stuck reversing valve, outdoor fan motor failure, and thermostat wiring problems are the usual suspects. Because a heat pump is also your air conditioner, a problem that shows up in winter can carry into summer if it's not fixed.
Repair or replace?
If your heat pump is older and needs a major repair, use the same repair-or-replace rules as for an AC. Replacing it means replacing both your heating and cooling, so get a proper load calculation.
Schedule heating repair and mention that you have a heat pump so the right technician comes out.