HVAC Troubleshooting

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Why Is My Heat Pump Not Cooling? Troubleshooting Tips

If you have an electric heat pump system in your home, you know it’s a workhorse year-round - heating your home in the winter and cooling it in the summer. But if you’re reading this, your air source heat pump is not working right. Don’t lose your cool - learn why your heat pump AC is not cooling and what you can do about it.

If doing a few simple things doesn’t get it blowing cold air again, call an HVAC professional.

#1: Check for power issues

If the heat pump will not cool, this may sound silly, but make sure there is power to the unit. Go outside and see if the heat pump is running but not cooling. That means power is not the issue, but something else is.

If the heat pump is not turning on at all, check the circuit breaker box. It may have tripped a breaker because something is wrong. If so, call for heat pump repair. Resetting the breaker and restarting the unit could cause damage.

#2: Check for thermostat issues

Next, check the thermostat. Incorrect settings may be to blame. Make sure the thermostat is set to Cool. If it got cold overnight, someone may have switched it to Heating mode. Make sure that the set temperature is lower than the current temperature in the house. Check that the fan is set to Auto and not On. You only want the fan to blow cool air when the unit is running.

If none of that gets the unit cooling your home, you need to check to see if the thermostat is communicating with the heat pump at all. Switch to Heat mode to see if the heat pump comes on. If it does, you may have a problem with the reversing valve (see #4.). If the heat pump does not come on, call for HVAC repair services. It could be a problem with your thermostat or your heat pump.

#3: Check for airflow issues

Heat pumps, like an air conditioner, need good airflow to work efficiently. If the flow of air is blocked, your HVAC system will struggle to reach the set temperature. First, check your HVAC air filter. If it’s dirty, change it. You should do this every 1-3 months depending on the quality of the filter. Refer to our air filter maintenance guide for more tips.

Check the outdoor unit and make sure it’s not surrounded by overgrown shrubs or ornamental plants. There should be at least two feet of clearance on all sides. Clear any debris off the top of the unit as well.

If your heat pump does not cool to the set temperature but cools a little, an airflow issue may be to blame. You should also check to make sure your registers and air return vents are not blocked.

It may also be worth having your ductwork checked for leaks. The heat pump may be working fine, but the cool air escapes from the ductwork before it gets distributed out through the registers. Leaky ducts can be to blame for the heat pump not cooling on hot days, or not cooling to the set temperature.

#4: Rule out reversing valve issues

Back in #2, we said if the heat pump works in Heat mode but doesn’t work in Cool mode, it may be a problem with the heat pump reversing valve. This heat pump component is in charge of regulating refrigerant flow. The refrigerant flows one way during heating mode and then the valve reverses the flow for cooling mode, and so on.

It is uncommon for this valve to get stuck. To see if this is the problem, you will need to contact an HVAC technician. Don’t try to troubleshoot this issue yourself - you could damage the valve and cause a refrigerant leak.

#5: Rule out low refrigerant

Another reason for your heat pump not cooling your house is the unit may be low on refrigerant. A low refrigerant level is more common with older units and improperly installed units. If the heat pump fan is running but it’s not cooling, low refrigerant could be the culprit.

The only reason a heat pump would have low refrigerant is if there is a refrigerant leak. If you suspect this is the problem, call an HVAC company right away to stop the leak and recharge the refrigerant. If it’s an older unit (more than 10 years old) you may want to start thinking about heat pump replacement, especially if you are having more frequent repairs. Check our Repair or Replace Guide for more information.

#6: Check for a frozen evaporator coil

Lastly, check for a frozen evaporator coil. This is the indoor coil in the air handler or a cabinet next to the furnace. A frozen coil can cause your heat pump to blow warm air in cooling mode. You may see visible icing at the indoor unit, or on the refrigerant lines at the outdoor unit.

A frozen evaporator coil can be caused by:

Dirty air filter
Dirty coil
Blocked return vents
Faulty thermostat
Refrigerant leak

If you have a frozen coil, turn the HVAC system off. Replace the filter if it’s dirty and call for HVAC repair. Be prepared for what you might pay for a repair service call by reading our blog on average heat pump repair costs.

Practice heat pump maintenance

Regular heat pump maintenance can help your unit perform as it should, all year long. Change your HVAC air filter every 30-90 days based on the quality of your air filter. Get some tips in our air filter maintenance guide.

Keep the outdoor unit clear - trim any grass or shrubs to at least two feet away for proper air circulation. Clear any debris such as leaves or twigs off of the top as well. If you get snowfall, clear snow off of the top of the unit. Consider purchasing the WeatherGuard™ Top Heat Pump Accessory to protect your unit. It helps keep out dust and debris and channels away rain and melting snow.

Schedule professional heat pump maintenance twice a year - before each cooling and heating season. Work with the original installer if possible - especially if your unit is under warranty.

Consider the benefits of Trane Diagnostics

Finally, if you have a Trane smart thermostat and the Trane Home App, consider opting into Trane Diagnostics. This gives your local Trane dealer remote monitoring capabilities that allow them to spot small problems before they become big ones.

Your smart thermostat sends real-time data that alerts the dealer to the need for maintenance or to a system malfunction. They can troubleshoot issues remotely and may be able to solve the problem remotely. If that’s the case, you would give them one-time dealer remote access (DRA).

If they need to schedule an in-person service call, the HVAC technician will arrive with the knowledge gained and will have the right parts. This saves time for both you and the HVAC company.

Anne Fonda, Content Writer at Trane Technologies

A Content Writer with Trane Technologies, Anne Fonda researches topics and writes for Trane® and associated residential HVAC brands. She works in collaboration with Trane Technologies subject matter experts, offering easy-to-understand, informative content on complex topics. Her goal is to help consumers make informed decisions on the products and services they need.

She has written for HVAC and other service provider websites for over 16 years. Before transitioning to web content writing, Anne had a 14-year stint as an award-winning journalist. She graduated cum laude from the University of Missouri-Columbia School of Journalism. When she’s not working, Anne enjoys playing word games, reading, gardening, spending time with family, and visiting gardens and museums.

Expert review by Mark Woodruff, Senior Product Manager, Ducted Outdoor