Heat Pump Blowing Cold Air? What's Normal, What's Not & How to Fix It
A heat pump blowing cold air in heating mode is often normal. During a defrost cycle it blows cool air for a few minutes, and even when it's working perfectly its air feels cooler than a furnace's. It's a real problem when the air stays cool for long stretches. Common causes are a thermostat set up wrong (often after a new smart thermostat), a failed defrost control, low refrigerant, or a stuck reversing valve. Repairs range from free to $1,500 to $3,500 for a reversing valve.
Typical pro cost
$150 to $650
- Urgency
- Soon in freezing weather
- DIY difficulty
- Easy checks first
- Time to fix
- 5 minutes to 4 hours
- Prices
- US typical range
Last reviewed October 2026
Is a heat pump blowing cold air normal?
Sometimes, yes. Before calling anyone, it helps to know three things heat pumps do that catch new owners off guard.
1. Its air is warm, not hot. A gas furnace sends out air at about 120 to 140°F. A heat pump's air is usually around 85 to 100°F. Your skin is around 90°F, so that air can feel cool on your hand, even while it's steadily heating the house. If rooms are reaching the thermostat setting, it's working.
2. It goes into defrost. In cold, damp weather, frost builds on the outdoor coil. Every so often, the heat pump briefly switches into cooling mode to melt it. That usually takes 5 to 15 minutes. You may see steam rising from the outdoor unit and hear a whoosh when it switches. Indoors, the air turns cool unless backup heat kicks in. That's normal.
3. It loses capacity in deep cold. As outdoor temperatures drop, especially below freezing, a standard heat pump moves less heat. Backup heat (also called "aux" or "emergency" heat) is meant to fill the gap. If the backup heat isn't working, the air turns lukewarm on the coldest days.
When a heat pump blowing cold air is a real problem
Thermostat set up wrong
Very common after a smart thermostat install. Heat pumps use an "O" or "B" setting to switch modes. Choose the wrong one and the system cools when you ask for heat. It's a free fix in the thermostat's settings.
Fan set to "On"
The blower runs between cycles, pushing room-temperature air that feels cold. Switch the fan to "Auto."
Dirty filter or blocked outdoor unit
Restricted airflow indoors, or snow and leaves packed around the outdoor unit, cuts heating capacity sharply.
Stuck in defrost, or never defrosting
A failed defrost board or sensor can leave the unit iced over, or stuck in cooling mode. See heat pump frozen.
Low refrigerant
A leak leaves the system unable to move enough heat. You'll notice weak heat, long run times and sometimes heavy icing.
Backup heat not working
Failed heat strips, a tripped heat strip breaker, or a sequencer that won't engage leaves you with cool air on the coldest days and during defrost.
Stuck reversing valve
The valve that switches between heating and cooling can stick in cooling. The system then cools all winter, blowing cold air inside and warm air outside.
Outdoor unit not running
If only the indoor fan runs, you get unheated air. Check the breaker and disconnect. See outside unit not running.
How to fix a heat pump blowing cold air, step by step
- 1
Set the thermostat to "Heat" and the fan to "Auto," with the temperature 2 to 3 degrees above the room. Replace the batteries if the screen is dim.
- 2
Go outside and look at the outdoor unit. If you see steam or the fan is stopped while ice melts, it's defrosting. Wait 15 minutes and check again.
- 3
Replace the indoor air filter, and clear snow, ice and leaves at least 2 feet around the outdoor unit. Make sure the top isn't buried.
- 4
If you recently installed a new thermostat, open its equipment settings. Check that it's set to "Heat pump" and that the reversing valve setting matches your system. Most Carrier, Trane, Lennox and Goodman systems use "O." Rheem and Ruud often use "B."
- 5
Check the main panel for a tripped breaker labeled heat pump, air handler, or "heat strips." Electric backup heat usually has its own large breaker.
- 6
Stand next to the outdoor unit while it runs in heat mode. Air coming out of the top should feel cool, because it's pulling heat out. Warm air blowing out of the top in heat mode means the system is cooling, which points to the reversing valve or the thermostat setting.
- 7
If the air indoors stays under about 75°F for more than 15 minutes and none of the above helps, switch to emergency heat to stay warm, and call a technician.
Tools and materials
- Kitchen thermometer for the vent test
- New air filter
- Broom or brush for snow
- Thermostat manual or app
Approximate DIY cost: $0 to $40
Call a pro when
- Warm air blows out of the outdoor unit in heat mode
- The outdoor coil stays iced for hours
- The backup heat breaker trips again after reset
- The air stays under 75°F outside defrost
- You suspect a refrigerant leak
Cost to fix a heat pump blowing cold air
| Job | Typical cost |
|---|---|
| Fix thermostat settings (DIY) | $0 |
| Service call or diagnostic | $75–$200 |
| Thermostat replacement | $85–$300 |
| Defrost sensor replacement | $150–$350 |
| Defrost control board replacement | $200–$600 |
| Backup heat strip or sequencer repair | $150–$600 |
| Reversing valve solenoid coil | $100–$350 |
| Refrigerant leak repair and recharge | $200–$1,600 |
| Reversing valve replacement | $1,500–$3,500 |
Ranges are typical US prices compiled by FixHomeCost from published cost guides. A stuck reversing valve sometimes just has a bad solenoid coil, a much cheaper part, so ask the technician to test the coil before replacing the valve.
Common questions
Why is my heat pump blowing cold air in heat mode?
It may be in a normal defrost cycle, or its 85 to 100°F air may just feel cool. If cool air lasts a long time, check the thermostat setup and fan setting, the filter and the outdoor unit. A failed defrost control, low refrigerant or a stuck reversing valve need a technician.
How long does a heat pump defrost cycle last?
Usually 5 to 15 minutes. You may see steam from the outdoor unit. If it lasts much longer, or the unit stays covered in ice, the defrost control may have failed.
Can a new thermostat make my heat pump blow cold air?
Yes, and it's very common. If the thermostat's reversing valve setting (O or B) is wrong for your system, it cools when you call for heat. Change the setting in the thermostat's equipment menu.
How much does it cost to fix a heat pump blowing cold air?
Most repairs cost $150 to $650, such as a defrost board, sensor or backup heat part. Refrigerant leaks run $200 to $1,600, and a reversing valve replacement $1,500 to $3,500.
Should I turn on emergency heat if my heat pump blows cold?
Temporarily, yes, to keep the house warm while you wait for a repair. It uses backup heat only, which usually costs much more to run, so don't leave it on as a long-term fix.
What temperature should air from a heat pump be?
Typically around 85 to 100°F at the vents in heat mode, cooler in very cold weather. That's lower than a furnace, which is why the air can feel cool even when it's working.
Related guides
This is general information, not a professional inspection. Electrical and refrigerant work requires a licensed technician. See how we research costs.