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Quick answer: If your heat pump blows cool air for a few minutes while steam rises from the outdoor unit, it is in defrost mode. That is normal. If it blows cold air for more than about 15 minutes, the outdoor unit is covered in a solid block of ice, or the outdoor fan is not spinning, your heat pump needs a repair.
Heat pumps are a great fit for Snohomish County winters. But the air they deliver feels different from a gas furnace, and that confuses a lot of homeowners. Here is how to tell normal from a real problem.
Heat pump air always feels cooler than furnace air
A furnace blows very hot air in short bursts. A heat pump delivers warm air for longer, steadier cycles. Put your hand at a vent and the air may feel lukewarm, even when the system is working perfectly. The real test is whether the house reaches and holds the temperature on the thermostat.
Defrost mode is normal
On cold, damp days, frost builds on the outdoor coil. Your heat pump clears it by running in reverse for a few minutes. During defrost, the outdoor fan stops, you may see steam and you may feel cooler air inside. Many systems turn on backup heat during defrost to keep you comfortable. Once the coil is clear, normal heating resumes.
Common causes of a heat pump blowing cold air
- Thermostat settings. The system is set to Cool or Auto, or the fan is set to On instead of Auto.
- A dirty filter. Low airflow makes the system work harder and deliver less heat.
- Ice that will not clear. This can point to a failed defrost sensor or control board, low refrigerant or poor drainage around the unit.
- A failed reversing valve. This part switches the heat pump between heating and cooling. When it sticks, the system can run but never heat. We replaced one for an Everett homeowner whose system ran all day without warming the house.
- Low refrigerant. This usually means a leak that needs to be found and fixed, not just topped off.
- Backup heat not working. On the coldest days, the auxiliary heat strips help your heat pump. If they fail, the house can fall behind.
What you can safely check yourself
- Set the thermostat to Heat and the fan to Auto.
- Replace the air filter if it looks dirty.
- Keep a couple of feet of space clear around the outdoor unit. Remove leaves, snow and debris.
- Never chip ice off the coil or pour hot water on it. You can damage the fins and refrigerant lines.
How Altitude Heating & Cooling fixes it
If those checks do not solve the problem, call Altitude Heating & Cooling. Our technicians diagnose and repair heat pumps across Lake Stevens, Snohomish, Everett, Marysville, Granite Falls, Monroe, Lynnwood and Mukilteo. We test the defrost controls, reversing valve, refrigerant charge, airflow and backup heat so we fix the cause, not just the symptom.
You get a clear explanation and the price before we start. If your heat pump is older and repairs no longer make sense, we will tell you honestly and walk you through replacement options, including cold-climate heat pumps built for our winters.
Heat pump blowing cold right now? Call 425-201-1998. We answer after-hours calls. For routine checks, book our $49 HVAC diagnostic and maintenance visit.
Frequently asked questions
How long should heat pump defrost last?
Usually a few minutes. If cool air and heavy ice last longer than about 15 minutes, call for service.
Is it normal for a heat pump to steam?
Yes. Steam from the outdoor unit during defrost is normal. Smoke or a burning smell is not.
Why is my heat pump running constantly in winter?
Heat pumps run longer cycles than furnaces, which is normal. If the house never reaches the thermostat setting, have it checked.
Can a frozen heat pump damage itself?
Yes. A heat pump that stays iced over can strain the compressor. Turn it to emergency heat and call for repair.
