Heat pump blowing cold air in winter: what it means

You set the thermostat to heat, put your hand over a vent, and the air feels cool. On a cold Phoenix morning, that's not what you want to feel.

Lots of Valley homes heat with a heat pump, the same outdoor unit that cools the house all summer. Our post on heat pump vs central air explains how it works. Here's what cool air in winter means and what to do about it.

Three reasons that aren't a breakdown

The air is warm, not hot

A gas furnace blows hot air in short bursts. A heat pump blows warm air for longer stretches. Against your hand, warm air can feel cool, even when the house is heating just fine.

The test is the room, not the vent. If the thermostat reaches the temperature you set, the heat pump is doing its job.

It's in a defrost cycle

On a cold, damp morning, frost can form on the outdoor coil. The heat pump clears it by running in cooling mode for a few minutes.

During that time you may feel cooler air inside and see steam rising from the outdoor unit. Both are normal. Warm air should come back on its own.

The fan is set to on

Check the fan setting on the thermostat. On means the fan runs all the time, even between heating cycles, so it blows room air across your skin.

Set it to auto. The fan will then run only while the system is heating.

One more setting to check: if you just put in a new thermostat, make sure it's set up for a heat pump. A thermostat set up for a furnace can't run a heat pump's heat mode the right way.

Signs it's a real fault

If none of the above explains it, something is likely wrong. These are the signs we look for.

Cool air that never warms up

If the air stays cool for more than a few minutes and the room keeps getting colder, the heat pump may be stuck in cooling mode. A part called the reversing valve flips it between the two, and it can stick.

Ice that stays on the outdoor unit

Light frost that clears is normal. A coil that stays coated in ice can't pull heat in. It often points to a defrost control fault, low refrigerant or a fan that has stopped.

The outdoor unit won't run

If the indoor fan blows but the outdoor unit sits silent, it isn't making heat. Check the breaker. If it trips again, leave it off and call us.

Emergency heat is always on

Many heat pumps have backup heat strips that kick in when the heat pump can't keep up. If the thermostat shows backup or emergency heat for hours on end, the heat pump isn't pulling its weight.

Those strips work like the coils in a toaster. They keep you warm, but your power bill will show it.

Loud noises from the outdoor unit

A whoosh when it switches into defrost is normal. A grind, a screech or a bang is not. Turn it off and call us before a small part takes a bigger one with it.

What to try before you call

1. Make sure the thermostat is set to heat, and a few degrees above the room temperature.
2. Set the fan to auto, not on.
3. Check the filter. A packed filter chokes the airflow and can make the system ice up.
4. Look at the outdoor unit. Clear away leaves, plants or anything blocking the sides.
5. Check the breakers for both the indoor and outdoor units.
6. Give it time. If it's a defrost cycle, warm air comes back within a few minutes.

If the house is still cold after all that, it's time for a tech. Switch to emergency heat to stay warm while you wait, if your thermostat has it.

On the visit, we test the heat pump in both heat and cool mode. We check the valve that switches between them, the defrost controls, the backup heat and the refrigerant. You see what we found and the price before any work starts.

Our heat pump repair page explains how we test both modes before we leave. If you heat with gas instead, our heating repair page covers furnaces. Most calls get a same-day visit with no emergency fee.