Short answer: Some cool air is normal. Carrier explains that heat pumps periodically run a defrost cycle of about 5 to 10 minutes that sends cooler air indoors, and that heat pump air is typically around 85 to 100°F compared with 120 to 140°F from a gas furnace. It is a problem if the air stays cold, the outdoor unit is covered in thick ice, or the system cools fine in summer but will not heat.
Quick diagnosis
| What you notice | Most likely cause | What to check | Call a pro? |
|---|---|---|---|
| Cool air for 5 to 10 minutes, steam from outdoor unit | Normal defrost cycle | Wait | No |
| Air warm but not hot | Normal heat pump supply temperature | Feel at a vent near the unit | No |
| Air cold all the time | Thermostat on Cool or fan ON | Set Heat and fan AUTO | If it continues |
| Thick ice (more than 1/4 inch) stays on outdoor unit | Airflow, refrigerant or defrost problem | Clear snow and debris around unit | Yes |
| Cools fine, will not heat | Stuck reversing valve | Note when it started | Yes |
| Outdoor fan not running | Power, capacitor or motor | Check outdoor disconnect and breakers | Yes |
Checks before you call
- Thermostat set to Heat, setpoint above room temperature.
- Check the breakers for both the indoor and outdoor units; call a pro if they keep tripping.
- Make sure the outdoor disconnect and the indoor air handler switch are on.
- Replace or clean the filter.
- Clear snow, leaves and debris; Carrier recommends keeping at least 24 inches of clear space around the outdoor unit.
- Reset: thermostat off, both breakers off for one minute, back on, wait a few minutes, then set Heat.
About emergency heat
Emergency (auxiliary) heat uses electric resistance strips or a backup furnace. It is useful if the outdoor unit fails, but Carrier warns it can raise your electric bill significantly, so use it only until the system is repaired.
Ice on the outdoor unit
A light frost under about 1/4 inch is normal and should clear during defrost. Heavy ice that remains, or very frequent defrosting, points to restricted airflow, low refrigerant or a defrost control problem.
When to call a professional
- The air stays cold for more than a defrost cycle.
- Thick ice stays on the outdoor unit.
- The system cools but does not heat.
- The outdoor fan does not run or the breakers keep tripping.
What it usually costs
HomeGuide (2026) puts general HVAC repairs at about $150 to $450. Refrigerant work on AC and heat pump systems commonly runs $100 to $600 for a recharge, plus leak repair if needed.
Frequently asked questions
Why does my heat pump blow cold air for a few minutes?
It is probably in defrost mode, which lasts about 5 to 10 minutes and is normal.
Should I use emergency heat?
Only if the heat pump is not working. It costs more to run.
Related problems
Sources
- Carrier: Heat pump not heating? Troubleshooting cold air
- HomeGuide: HVAC repair cost (2026)
- HomeGuide: AC repair cost (2026)
This guide is general information, not a substitute for an inspection by a licensed professional. See our disclaimer.