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Heat pump not heating? What's normal in winter and what isn't

General home information from Prufloop. Updated October 28, 2026.

The short answer. Heat pumps make air that feels cooler than a furnace's, and in cold weather they run defrost cycles where the outdoor fan stops and the unit steams for a few minutes. That's normal. It's a problem if the house can't stay warm, the outdoor unit stays coated in ice, the system runs on emergency heat constantly, or the outdoor unit doesn't run at all.

What you can safely check

Make sure the thermostat is set to Heat (not Emergency Heat unless you need it) and the setpoint is above room temperature.
Replace a dirty air filter.
Check the outdoor unit: light frost that clears during defrost is normal; a solid block of ice is not.
Clear snow, leaves or anything blocking the outdoor unit.
Check the breakers for the indoor and outdoor units.

When to call a HVAC tech

The outdoor unit stays iced over
The house won't get warm, or the thermostat shows auxiliary heat running all the time
The outdoor unit doesn't run
You hear grinding or loud banging

What a HVAC tech will usually do

Tests the defrost controls, sensors and reversing valve
Checks refrigerant charge
Checks auxiliary heat strips and thermostat wiring

Asking an AI assistant to book it

Once Prufloop launches (planned for Q4 2026 around Charlotte), you'll be able to ask the AI assistant you use something like this, and it can book a verified pro at a posted price in a real open slot. This is how it's planned to work; no assistant is connected yet.

Example request. “My heat pump is blowing cool air and the outdoor unit is a block of ice. Book a licensed HVAC tech in Indian Trail as soon as one is open.”

Before a job is booked, you see the pro's posted price, including any trip or diagnostic fee. Anything extra needs your OK first. When the work is done, you confirm it's fixed with a quick text. That's Proof of Done™.

Questions

Why is my heat pump steaming?

That's usually a normal defrost cycle melting frost off the outdoor coil.

When should I use emergency heat?

Only when the heat pump itself isn't working and you're waiting on a repair. It's usually much more expensive to run.

Can my AI assistant book a HVAC tech for this through Prufloop?

Not yet. Prufloop is being built so the AI assistant you already use can book a verified HVAC tech at a posted price, starting with the Charlotte-area pilot planned for Q4 2026 in Mecklenburg, Union, Cabarrus, Iredell, Gaston and Lincoln counties in North Carolina, plus York and Lancaster counties in South Carolina. No AI assistant is connected yet.

Are you a Charlotte-area HVAC tech?

Free to join. Only pay on jobs completed: 10% on jobs under $2,500, less on bigger jobs, charged when the job is marked done. No lead fees. Founding pros get a guaranteed spot and founding terms locked for 24 months.

Secure your spot

How it works for pros