Heat pump not cooling: the most common problems and solutions

Reviewed by Eric Grubbs

As summer temperatures ramp up, a heat pump not cooling your home is the type of problem you want to remedy right away. There are a number of problems that could cause your heat pump to malfunction, so we’re exploring the most common scenarios.

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While we dive into why your heat pump won’t cool, keep in mind there are some solutions safe for a DIY job but others need to be handled by a professional heat pump repair technician. Consider whether one of these most common heat pump problems could be the culprit behind your disabled unit.

The 4 most common heat pump problems

Heat pump not turning on

If your heat pump won’t turn on at all, there are four likely causes to consider.

  • Start with the thermostat. Ensure that the device is displaying correctly and is set to “cool” with the desired temperature below the home’s current indoor temperature. If you have a smart thermostat, check for any system error messages or alerts. The technology within these smart devices will often alert you to potential problems.
  • Ensure the unit is receiving power. A heat pump demands a large amount of power to start up and maintain operation. If the unit pulls too much power at once, the circuit breaker can trip as a safety precaution. Check the electrical panel and switch the heat pump breaker to “on” if necessary. If the breaker continues to trip itself off, there’s a bigger issue at play. Contact a heat pump technician right away for service.
  • The heat pump start capacitor is broken. Take a moment to listen to your heat pump. If you can hear a faint clicking noise that occurs as the heat pump is supposed to turn on, your problem is likely with the start capacitor. This component holds an electrical charge that is released when the motor tries to start and helps the motor start with less effort. You’ll need to bring a technician out to replace it.
  • The reversing valve isn’t reversing. As the name suggests, the reversing valve allows the heat pump to work as both a heater and an air conditioner by reversing the direction of the refrigerant. Most manufacturers design their systems to default to heat, meaning if the reversing valve is not working properly only heat will be delivered. Rheem and RUUD are the two brands that default to cooling. If your unit is only delivering warm air (or cool air for Rheem and RUUD users), a technician will need to repair or replace the reversing valve.

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Heat pump not heating

During the summer, your primary concern will be addressing any malfunctions that result in your heat pump AC not working. However, if your heat pump is not blowing hot air in the winter, explore these three main causes:

  • The unit is blocked. The heat pump pulls heat from the outside air into the system’s refrigerant, and the refrigerant carries that heat to the indoor coil, heating the air in your home. If the airflow to your unit is blocked by snow, ice, leaves or another type of debris, this can make it hard for the heat pump to do its job. Luckily, the solution is simple. Clean off your heat pump and clear away any debris that may be blocking the way.
  • Debris is clogging the air filter. Air filters are put in place to catch dirt and debris, but when too much builds up, it can block airflow to to indoor coil, which is responsible for heating the air. Routinely check your filter and change it out for a new one if it’s dirty.
  • Refrigerant level or charge is low. If your refrigerant levels are too low, likely from a leak, your heat pump will struggle to bring enough heat indoors to heat your home. Have a professional come out to check if the levels are too low or your system needs to be recharged. Refilling and recharging the refrigerant level must be done by an EPA-certified HVAC professional.

Heat pump not cooling

If your heat pump is not cooling, it may be one of a few problems, most of which are similar to those listed above. When your heat pump is not blowing cold air, the temperature in your home can rise quickly and create an uncomfortable environment. It is often the case that the same problem that is causing your heat pump not to cool your home, can also be the reason your heat pump isn’t able to heat your home.

  • Check the thermostat settings. Is the device set to “cool” with the desired temperature? If all settings are correct, it’s possible the thermostat isn’t reading the indoor temperature correctly or an electrical problem is preventing the device from communicating with the heat pump. You’ll need a professional heat pump technician to fix either of these problems, so continue to troubleshoot heat pump not cooling options before you call in the pros.
  • The reversing valve is not working properly. If your heat pump is running, but the air coming out of your vents is hot, it’s likely a problem with your reversing valve. Again, this is the part of the heat pump that reverses the refrigerant and allows it to act as both a heater and an air conditioner. If this component fails, it will need to be replaced or repaired by a technician.
  • The components are dirty. When air flow is limited, the system cannot function properly. Lukewarm air expelling from your vents most likely points to dirty or clogged heat pump components. Remove debris from around the outdoor unit and check to see if your filters need to be replaced.
  • Refrigerant level or charge is low. If your refrigerant levels are too low or if there is a leak, your heat pump will struggle to cool your home. Routine maintenance is the best preventative measure for identifying refrigerant problems or potential leaks.

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Heat pump running constantly

A heat pump that’s running constantly will create a spike in your energy bill and shorten the lifespan of your unit. Some of the causes may be within your control. The most common reasons heat pumps don’t shut off include:

  • Thermostat settings are extreme. It’s understandable that you want to keep your home cool in the summer and warm in the winter, but if the thermostat is set too high or low, the unit will work continuously to try to achieve your desired temperature. Use these thermostat tips to help manage energy use.
  • The air filter is dirty. Without a continuous flow of air, the heat pump can’t cool or heat your home efficiently. Filters typically need to be replaced every 90 days, but it’s good practice to check the cleanliness of your filter each month so you can replace it sooner if needed.
  • The compressor contactor is not working properly. The compressor contactor controls power to the compressor and the outdoor fan on your heat pump. If that’s damaged, it’s possible your heat pump could run all the time. You’ll need a professional to repair or replace the part.

Trane heat pump troubleshooting

Trane heat pumps are backed by one of the best warranties in the industry. When troubleshooting potential problems with a Trane unit, the manufacturer suggests ensuring your thermostat is set to 78 degrees in the summer and 68 degrees in the winter. This helps the unit complete its heating and cooling cycles less often and avoids the heat pump from operating continuously.

A tripped circuit breaker or worn out wiring could also be to blame for your Trane heat pump not working properly. A certified Trane dealer can inspect your unit for worn or defective wiring.

Trane also warns you could have a defective defroster timer or control module if you experience ice build up on the outdoor coil of the heat pump.

Carrier heat pump troubleshooting

Backed by a limited 10-year warranty, Carrier heat pumps come in a variety of models. While the specific repair will depend on the types of unit you have, the manufacturer does offer some general troubleshooting tips if the heat pump won’t cool.

One of the most obvious signs of heat pump malfunction in the summer is the indoor coil freezing. If frost has started to form on the Carrier unit, turn the heat pump off and allow time to thaw. This process may take up to 24 hours without the help of a professional. It’s likely there is an airflow issue, which calls for an HVAC technician to make the repair.

Carrier also warns that a blown blower motor, defective fan motor, or compressor issue could be to blame for a heat pump failure.

Goodman heat pump troubleshooting

Goodman heat pumps are noted for their energy efficiency and value for those sticking to a home improvement budget. There are a number of models to choose from and homeowners can customize their warranty by purchasing extended coverage for the new unit.

Goodman suggests the best way to prevent having to troubleshoot your heat pump system is by scheduling seasonal maintenance visits with an HVAC expert. The manufacturer says because heat pumps are used in the heating and cooling seasons, the best upkeep plan includes a unit check-up in the spring and fall.

Size also matters. Ensuring the heat pump is appropriately sized for your home will ensure heating and cooling cycles run appropriately and your energy bills are manageable.

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Lennox heat pump troubleshooting

Lennox heat pumps offer a wide scale of SEER ratings, models, and warranty options. Depending on what matters most to your family, several units are designed with ultra-quiet operating systems.

If any component of your unit fails, Lennox recommends starting with basic facts to determine if it’s best to repair or replace your broken heat pump. Knowing the age, cost of repair, and the current system’s energy efficiency will help you make the best investment decision for your home.

Hire a heat pump technician

If you’ve walked through the homeowner evaluation tips listed above but can’t determine why your heat pump won’t cool, it’s time to call on a professional HVAC technician. Use our tips while vetting and hiring a company.

Frequently asked questions

What problems should you expect with a heat pump that’s been left unused?
A heat pump that’s left unused could experience any of the problems listed above, but it’s particularly susceptible to problems caused by debris and refrigerant leaks.  
What problems affect a heat pump’s air handler?
If your system’s fan is running, but only cold air is coming out, it may be a problem with your air handler. If you’re hearing rattling noises from your system, it may also be the air handler.
How do I diagnose heat pump problems?
You can diagnose problems using some of the DIY fixes above, or by comparing heat pump reviews for your specific model. The best way to diagnose and treat any problems is to call in a local heat pump professional.