Heat pump blowing cold air?

Cool air for a few minutes can be normal: the heat pump briefly switches into defrost mode in cold weather. If the air stays cool, the cause is usually a thermostat setting, a dirty filter, or a refrigerant or valve problem.

Not sure which one it is? Snap your heat pump and we’ll narrow it down.

Is the house just staying cold, with no obviously cool air?

That's the broader not-heating problem. Heat pump not heating

Likely causes

  1. Defrost mode (normal)

    Most commonEasy DIY

    Cool air for roughly 5–15 minutes, steam or vapor rising from the outdoor unit, and the outdoor fan stopped, in cold or damp weather. It repeats every hour or so and the air warms up again. Nothing is wrong.

  2. Thermostat set wrong, or fan on instead of auto

    Most commonEasy DIY

    Set to Cool, or the fan set to On, which blows room-temperature air between heating cycles. A dead battery or an unexpected schedule can do the same.

    Part: $5–15 (batteries)

  3. Clogged air filter or blocked vents

    CommonEasy DIY

    Weak airflow, a filter caked with dust, or air that's only lukewarm. Restricted airflow can also ice the indoor coil.

    Part: $10–40 (filter)

  4. Iced outdoor unit or very cold weather

    CommonCall a pro

    Heavy ice that won't clear, or outdoor temperatures below the unit's effective range, where it can't pull enough heat from the air. Many homes then rely on aux heat strips; if those don't come on, the air stays cool.

    Part: $150–700 (installed)

  5. Low refrigerant, stuck reversing valve or failed compressor

    Less commonCall a pro

    Air that stays cool in mild weather, the system acting as if it's in cooling mode, or hissing and oily residue on the refrigerant lines.

    Part: $100–2,500 (a recharge at the low end, a compressor at the top)

Quick checks

Turn the system off at the thermostat and the breaker before touching anything on the outdoor unit, and never reach into the fan. Don't chip ice off the coil or fins; you can puncture the refrigerant line. Refrigerant and electrical work need a licensed technician. If you smell burning or see smoke or sparks, switch the breaker off and call a pro.

  1. Wait 15–20 minutes. If the air warms back up and the outdoor unit had steam coming off it, that was defrost mode.
  2. Check the thermostat is on Heat (not Cool), the fan is on Auto, and the set temperature is above the room temperature.
  3. Replace the air filter if it's grey and clogged, and open every supply vent.
  4. Look at the outdoor unit: clear debris from around it, but don't chip at ice or poke the coil.
  5. If the thermostat shows Em Heat, someone switched it to backup heat by hand, so switch it back to Heat. If it shows Aux, the backup is helping on its own, which is normal in very cold weather; call a pro if Aux stays on in mild weather.
Sharpen the read

Diagnose your heat pump in seconds, for free

No account, no phone number. Fixology’s AI reads your photo and tells you what’s likely wrong, how worried to be, and whether it’s a DIY fix.

Snap one of these:

  • the thermostat display, including the mode and fan setting
  • the outdoor unit, especially any ice or steam
  • the model label on the side of the unit

Add a note or more photos next. Nobody calls you.

When to call a pro

The air stays cool for more than about 20 minutes, defrost seems to run constantly, ice stays on the outdoor unit, you hear hissing or grinding, or you see oily residue on the lines. For lifespan and upkeep, see the heat pump guide.

Typical cost: $150–650 for most repairs including the service call (about $400 on average). A diagnostic visit typically runs $75–250, often credited if you go ahead. A compressor replacement can reach $2,500.

Sources: Fixr: How Much Does Heat Pump Repair Cost in 2026? (updated January 21, 2026)

After a scan, Fixology can also help you find pros near you.

Related problems

  • Heat pump not heating?

    Heat pump

    The heat pump runs but the house stays cold, which is usually thermostat settings, a clogged filter, or an iced-over outdoor unit.

  • Furnace won't heat?

    FurnaceFall

    The furnace runs but the house stays cold, which is usually a clogged filter, a thermostat setting, or an ignition fault.

  • Washer won't drain?

    Washer

    Water is left in the drum after the cycle, which is usually a clogged pump filter or a kinked drain hose.

  • Fridge not cooling?

    Fridge

    The fridge section is warm or warming. The cause depends on whether the freezer is still cold, and the first fix is often free.

Fixology helps you understand your home — it isn't a substitute for a licensed pro on serious gas, electrical, or structural work.