Why Your Heat Pump Isn’t Heating—and What You Can Do to Fix It

Keeping your home warm is essential in the fall and winter months, so when the heat pump isn’t heating and blows cold air when it should be blowing warm air, pinning down your heat pump problem’s source becomes top priority. You wouldn’t be faulted for immediately calling in the pros, but you might be able to fix the issue on your own with a little know-how.

Summarizing how a heat pump works, Adam Ross, South Florida Academy of Air Conditioning Executive Director and owner of Aircon Repair in Fort Lauderdale, Florida, explains, “A heat pump transfers heat between indoor and outdoor air. It uses refrigerant to absorb heat from the outside air (even in cold weather) and moves it inside to warm the home. In cooling mode, it reverses the process, extracting heat from the indoor air and releasing it outdoors.” 

If your heat pump isn’t warming your home like it should, that means one or more parts of the above process aren’t working correctly and that it’s time to diagnose the issue. Below are some of the most common causes for a heat pump that’s not heating. Once you’ve identified your problem(s), there are several ways to fix a heat pump—either on your own or, in certain cases, with the help of an HVAC professional.

The refrigerant is low or leaking.

For a heat pump to function properly, the refrigerant should be filled to the appropriate amount. However, if the refrigerant line has a leak, then the system can lose its ability to effectively transfer heat from one area to another. This also means that during the warmer months of the year, a heat pump that isn’t cooling may have low or leaking refrigerant, as well.  

“Handling refrigerant requires special tools and knowledge due to environmental risks,” advises Ross. So if you suspect that the heat pump not heating is due to low refrigerant levels or a leaking refrigerant line, you will need to contact a local HVAC company for repairs.

The air filters are dirty and clogged.

Clogged air filters are a common HVAC problem, so regardless of whether you have a heat pump or furnace, it’s worth inspecting the air filter for blockages. Air filters trap hair, dust, dirt, and other debris, passively cleaning the air before it’s blown into the home, but if the heat pump is not working, it could be due to debris accumulating to the point of clogging the air filter. 

If your air filter is older than 90 days, replace it with a new one if you have an extra on hand. Otherwise, wipe the filter off as best you can with a microfiber cloth, suck up any remaining debris with a handheld vacuum or vacuum attachment, thoroughly rinse it under warm water, and reinstall it after allowing it to fully dry.

Preventing this issue from reoccurring is relatively straightforward: Simply check the air filter once a month and plan to clean or replace it about once every three months. This basic maintenance step will keep the heat pump system functioning efficiently and reduce the risk of future filter-related issues.

There is an issue with the thermostat.

An often-overlooked source of a heat pump not blowing hot air is the thermostat. Most homeowners will figure that the issue is with the actual unit, without checking the current settings on the thermostat—but even the best heat pump will still blow cold air in the winter if the temperature is set low enough. So, before contacting an HVAC company, check the current thermostat settings and make adjustments if necessary.

Alternatively, the thermostat can become uncalibrated due to a sudden impact, like someone bumping into it or dirt buildup inside the device. This can cause the thermostat to be off by a few degrees, leading to a heat pump that blows cold air when it’s set to heat. To resolve this issue, recalibrate your thermostat by following the directions in the unit’s operations manual or contact an HVAC pro to recalibrate the thermostat for you.

The unit is blocked or frozen.

A heat pump requires space around the outside unit so it can pull air into your home, but if the unit is blocked, this can prevent the heat pump from operating properly. Clear away any snow, ice, or leaves that may have built up around the outdoor unit, and move nearby items that could be restricting airflow.

Similarly, if the outdoor unit is frozen, then it won’t be able to transfer heat to the inside of the home. Check the outdoor unit for any ice or frost on the copper tubing or coils. While most heat pumps have an automatic defrosting function, you should try to clear some of the ice by turning off the heat pump system at the circuit breaker and running warm water across the sides of the heat pump. If the issue continues, contact a professional HVAC contractor to assess and resolve the situation. 

The system has a faulty reversing valve.

One of the features that makes a heat pump worth the cost is that it is capable of both heating and cooling. However, for the system to switch between those functions, it uses a device known as a reversing valve. If the reversing valve on the heat pump system is faulty, the heat pump won’t be able to switch from cooling to heating, which could be the reason why your heat pump is blowing cold air into the home. 

An issue with the reversing valve can also cause the heat pump to blow hot air into the home during the warmer months. To fix a faulty reversing valve, you will need to have a trained HVAC professional confirm that this is the source of the problem and replace the valve on the system. Once this is complete, heat should be restored to the home. 

There is a problem with the power. 

Heat pumps require power to operate, so if there is an issue with the power source, like a short or a tripped breaker, it can cause problems with the heat pump. Additionally, both the indoor and outdoor units have individual power switches, so you need to ensure that both switches are in the on position for the heat pump to function properly.

Check the power switch on the indoor air handler, then head outdoors to check the switch on the exterior of the home, close to the outdoor unit. If both switches are on, there may be a tripped breaker or a blown fuse. Inspect the fuses for the outdoor unit, then go inside to check the breaker box. Resetting the breaker may resolve the issue, but if the outdoor fuses are blown or if the breaker keeps tripping, contact an HVAC pro to assess and repair the problem. 

Troubleshooting a Heat Pump That’s Not Heating

Before contacting your local HVAC company to handle when the heat pump does not heat, you might be able to identify the problem and, depending on the heat pump issues you discover, conduct repairs yourself. Ross suggests these steps to follow for heat pump troubleshooting:

1. Check thermostat settings: Ensure the thermostat is set to “heat” and the temperature is correctly adjusted.
2. Inspect air filters: Replace dirty filters, since restricted airflow can affect heating.
3. Check the power supply: Make sure the unit has power by checking the circuit breaker or fuse.
4. Inspect the outdoor unit: Look for ice buildup, debris, or blockages. Defrost if necessary and remove any obstructions.
5. Inspect for refrigerant leaks: Low refrigerant can prevent the system from heating effectively, but this often requires a professional to fix.

If you have gone through each of these steps and still the heat pump will not heat, then it’s recommended to contact an HVAC professional. HVAC and AC repair costs are typically reasonable, depending on the problem, though it’s worth researching and comparing prices from several reputable companies in the area.