Heat Pump Blowing Cold Air? 6 Causes, Including the One That’s Perfectly Normal

Late October is when heat pumps in Northern Virginia switch from cooling to heating for the season. The first frosty mornings bring a lot of questions about cool air from the vents. Some of those systems are working exactly as designed. Others have a real fault, and catching it now beats finding it on the first night in the teens.

First, is the air actually cold?

A heat pump heats differently from a gas furnace. A furnace burns gas and sends out very hot air in short bursts. A heat pump moves heat from the outdoor air into the house, so its air is warm but milder, and the system runs longer cycles to keep up. Air that’s warmer than the room can still feel cool against your hand, especially near a vent where the air is moving fast.

For a quick test, stand near a supply vent after the system has run for 10 minutes. Air that feels about as warm as your skin or warmer is usually fine. If it feels like the room or colder, you have a heat pump blowing cold air for one of the reasons below.

Heat pump blowing cold air: 6 common causes

1. The heat pump is in defrost mode

You can fix this

On cold, damp days, frost builds up on the outdoor coil. The heat pump clears it by briefly reversing into cooling mode, which warms the outdoor coil and sends cooler air indoors. American Standard says its demand-defrost systems usually take 3 to 5 minutes, that you may see a cloud of steam from the outdoor unit, and that AUX may show on the thermostat during defrost. All of that is normal. A heat pump blowing cold air for a few minutes, then going back to warm, needs no repair.

2. The thermostat is set wrong

You can fix this

After a summer of cooling, the mode is often still on COOL. Set it to HEAT and set the temperature a few degrees above the room. Then check the fan. With the fan set to ON, the indoor blower runs nonstop, including between heating cycles, and that air feels cool. Set it to AUTO so the blower only runs while the system is heating. If your thermostat is blank or acting up, see our thermostat repair page.

3. A dirty filter or blocked returns

You can fix this

A clogged filter cuts airflow across the indoor coil. The system runs, but less heat reaches the rooms, and the weak stream of air feels cool. The U.S. Department of Energy says to clean or change heat pump filters every 3 months or as the manufacturer recommends. While you’re at it, move rugs and furniture off the return grilles, the larger vents that pull air back to the system.

4. The outdoor unit is blocked by leaves, snow or ice

Maybe a DIY fix

The outdoor unit needs open airflow to pull heat from outside. Fall leaves, a pile of mulch or drifted snow against the coil can choke it. Turn the system off at the thermostat, then clear leaves and snow by hand and keep about 2 feet open on every side. A light coat of frost that comes and goes is normal. A unit that stays coated in thick ice, or keeps switching into defrost with longer and longer cycles, needs a technician. Don’t chip at the ice, because the coil fins bend and puncture easily.

5. Low refrigerant or a stuck reversing valve

Call a technician

A heat pump that runs steadily but never warms up may be low on refrigerant, which means there’s a leak somewhere in the system. The DOE notes that too much or too little refrigerant reduces heat pump performance. Another cause is the reversing valve, the part that switches the system between heating and cooling. If it sticks in the cooling position, the heat pump blows cold air the whole time it runs. Both are sealed-system work that needs an EPA 608 certified technician, and our techs are certified.

6. The outdoor unit or the backup heat isn’t running

Call a technician

If the indoor fan runs but the outdoor unit is silent, the system can’t make heat. Check the breakers for both the indoor and outdoor units. If one is tripped, you can reset it once. If it trips again, leave it off and call. A failed capacitor, contactor, fan motor or compressor inside the outdoor unit needs a technician. On very cold nights, most heat pumps also use backup electric heat strips, shown as AUX or EM HEAT on the thermostat. If those strips fail, the air can turn lukewarm when the temperature drops.

When to call a technician

Call us about a heat pump blowing cold air if any of these are true:

• The air is still cool after you fixed the thermostat settings and changed the filter
• Cool air lasts longer than about 15 minutes, or keeps coming back
• The outdoor unit is iced solid, or the fan and compressor don’t run
• A breaker trips again after one reset
• You hear grinding, screeching or loud buzzing from either unit

Heat pump repair in Northern Virginia

Cool air from the vents is a common worry when the first frosty mornings arrive. Woodland handles heat pump repair across Prince William, Fairfax, Loudoun and Fauquier counties, plus Arlington and Alexandria. We’re based in Woodbridge, so Woodbridge, Manassas, Dumfries and Lorton are usually same-day calls, and we’re in Fairfax, Centreville, Springfield, Arlington and Alexandria every week. See our heat pump repair page or call (703) 335-1009.

What a visit costs with Woodland

You get a flat quote before any work starts. If you’d rather catch problems before winter, book our $99 heating tune-up. Our HVAC repair team handles both indoor and outdoor units.

Same price any day we’re open, including evenings and Saturdays. There’s no travel fee.

Frequently asked questions

Why is my heat pump blowing cold air in the morning?

On cold, damp mornings the outdoor coil frosts over and the heat pump runs a defrost cycle. You may feel cool air for a few minutes and see steam from the outdoor unit. That’s normal, as long as warm air comes back soon after.

How long should a heat pump defrost cycle last?

Most defrost cycles last a few minutes. American Standard says its demand-defrost systems usually take 3 to 5 minutes. If cycles keep getting longer or the unit stays covered in ice, call a technician.

Is a heat pump blowing cold air an emergency?

Usually not. Check the thermostat, filter and outdoor unit first. If the house is losing heat on a freezing night, or a breaker keeps tripping, call us the same day.

Should I switch my heat pump to emergency heat?

Emergency heat runs only the backup electric strips. It can keep the house warm until a technician arrives, but it uses much more electricity. Use it as a short-term fix and call for service.

Can you fix a heat pump blowing cold air the same day?

We can usually be there the same day in most of Prince William and Fairfax counties, so call early. The visit is a $69 diagnostic, waived with the repair, with a flat quote before any work.

Keep reading

Furnace Not Turning On the First Cold Day? What to Check, the Reset Button Question, and Which Burning Smells Are NormalHeating & furnacesFurnace Blowing Cold Air? 7 Common Causes and What to Check FirstHeating & furnacesIs Your Heat Pump Running All Night? We Tested What Happens as Outdoor Temperatures Keep DroppingData & experiments