Heat Pump Not Cooling? Why Is My Heat Pump Blowing Hot Air

A heat pump blowing hot air in summer isn’t doing you any favors.

Why is the heat pump not cooling?

Heat Pump Blowing Hot Air: Problems and Solutions

Here are the top 6 possible reasons your heat pump isn’t cooling.

It Isn’t In Cool Mode

Oops! If the thermostat is still set to Heat or Fan-only mode, you’ll have a heat pump blowing hot air – or air that is warm at best.

You wouldn’t be the first homeowner to overlook this obvious one. Not by a long shot!

It could be the thermostat.

If it’s in Cool mode, but you’re still getting air that definitely hasn’t be air conditioned, it might be a broken thermostat.

If the thermostat is old, considering replacing it. Thermostats cost as little as $20 but can range to hundreds of dollars.

Our Thermostat Buying Guide should prove useful as you consider a new thermostat that has the features and convenience you want.

We’ve reviewed all the smart thermostats too – Nest, ecobee, Lyric, Lux and others including the latest generations of them. Use our search box to locate our review of the brands you are considering.

If the thermostat is newer, go through the rest of this checklist for a heat pump not cooling.

The Air Filter is Dirty

This is another simple fix to a heat pump not cooling.

When the filter is dirty, it restricts airflow. Even if the heat pump is cooling the air, that air might not be making it into your ductwork and the living spaces of your home.

Air Filter Cleaning Tips

The best thing to do is to replace the air filter. We have written an in-depth buying guide of air filter, check it here. But if you don’t have an extra on hand, here are two options.

Brush off the thick layer of debris from the air filter with your hand or a soft brush. Give it a gentle shake, and tap it on the ground.

These tasks are best done outside with you holding the filter downwind.

If it’s super dirty and you can’t get much debris off it, your HVAC system will be OK without a filter for a short time.

Get a new filter and install it in the next day or two.

The Heat Pump is Low on Refrigerant

This is the top mechanical reason for a heat pump not cooling. It is usually the result of a refrigerant leak.

Refrigerant captures heat inside your home through the indoor coil. A refrigerant line carries hot refrigerant outside where it enters the radiator-style outdoor coil. There, the heat is released and dispersed by the heat pump fan.

When the refrigerant charge is low, there isn’t enough refrigerant to do its job. Hence, you get very poor cooling or no cooling at all.

Repairing a Refrigerant Leak

It requires a license to handle refrigerant and special equipment to know when the system is properly charged.

An HVAC technician also has a sensor to locate refrigerant leaks. If the leak is at a fitting, the repair might cost $250 or less.

If the tubing in the coil is leaking, coil replacement is a repair in the $600 to $2,000+ range.

See the section below on Repair vs Replacement options and tips.

The Coils are Dirty

Dust, grass clippings, pet hair and a thousand other types of debris cling to coil fins.

For the indoor coil to collect heat and the outdoor coil to disperse heat as effectively as possible, they must be clean of debris.

How to Clean a Heat Pump Coil

Cleaning an outdoor coil can be done with a hose – but not a pressure washer. Gently rinse away debris from the coil. Stubborn debris can be removed with a light bristle brush or a soft paint brush, the kind used for house painting.

Cleaning an indoor coil is often more difficult since it is harder to get to. Most homeowners leave this work to an HVAC technician. Cleaning both coils is usually part of a comprehensive maintenance service.

The service ranges from $75 to $200 based on how many items are on the checklist.

If you’re a thrifty and handy homeowner, you can DIY. This video gives a demonstration. The technician calls it an evaporator unit, just another name for the indoor mechanics of a heat pump.

The Indoor Coil is Frosted

The coil in your air handler or furnace gets extremely cold when your system is in Cool mode. Plus, it condenses moisture out of the air to dehumidify your home.

A super-cold coil + condensation = frost

The buildup will prevent it from gathering heat and produce a heat pump blowing hot air instead.

Some heat pumps can defrost the indoor coil. They do this by reversing the refrigerant flow to pick up heat outside, as if in Heat mode, and bring it in to defrost the coil.

The Frost Fix

It might take 30 minutes or more to defrost a coil, so give it some time.

After 30-45 minutes of warm air, you can try this solution: Turn your system to Fan mode.

This will pull air from in your house over the coil. It will be warm enough to defrost the coil.

A Valve Has Failed

There are several valves that direct the flow of refrigerant through the system. These include the reversing valve, thermal expansion valve (TXV) and valves in both coils that regulate the flow of refrigerant.

Heat pumps don’t make heat. They just move it.

The reversing valve changes the flow of refrigerant to collect heat indoors and carry it our (air conditioning mode) or the reverse (heating mode).

The valves are supported by electric components such as solenoids.

If the fixes so far haven’t helped, a bad valve is a likely suspect.

Valve Replacement is Best Left to Pros

It’s the diagnosis that is difficult. Plus, replacing a valve often requires adding refrigerant to the system.

Since a refrigerant license and pressure testing equipment are required, the job is best left to a qualified heat pump technician.

Depending on the valve needing replacement, the repair will range from about $175 to more than $500.

More on Heat Pump Repair Cost

The repair costs in our AC Repair Guide are quite similar to heat pump repair costs.

They will help you decide if repair is the right option or if it might be better to use the money toward a new heat pump.

Heat Pump: Repair or Replace?

If your heat pump is under warranty and hasn’t had issues, repairing it makes sense.

When it starts to get older – like 12+ years and/or has had several costly repair issues already –replacing is attractive.

Maybe ‘attractive’ is not the right word, since the cost will be $3,000 to $6,000 depending on the heat pumps quality and size.

However, spending $300-$500 per repair on several repairs and then having to replace it anyway in a few years is downright ugly. 

Get estimates for both! We recommend talking with several heat pump installers about the issue. They will give you both repair and replacement estimates to compare.

Fast and easy. If you’d like a quick and convenient way to get these estimates, our Free Local Quotes offer comes with no cost and no obligation to accept any of the estimates.

The contractors are licensed and insured, and they know that they are competing for the work.

Using the service is a great way to get repair and replace estimates from proven professionals in your area.

More information about heat pump could be found in our Heat Pump Buying Guide

Written by

Rene has worked 10 years in the HVAC field and now is the Senior Comfort Specialist for PICKHVAC. He holds an HVAC associate degree and EPA & R-410A Certifications.

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