12 Reasons Why Your Heat Pump is Blowing Cold Air in Heat Mode

Are you frustrated by your heat pump blowing cold air when you expect cozy warmth? You’re not alone! As the season changes and temperatures drop, many homeowners encounter this perplexing issue with their heating system.

Identifying and understanding the cause of this problem is the first step to resolving it. There could be a number of reasons why cold air is blowing from your heat pump in heat mode – clogged air filters, frozen coils, or malfunctioning valves are all common culprits. Some simple maintenance tasks like checking and replacing filters and cleaning outdoor condenser units help get things running smoothly again.

This blog will guide you through the simple fixes you can do for yourself and the more complex problems that require a professional’s help.

How Does a Heat Pump Operate?

Typically, a heat pump functions using the principles of heat transfer. It does not create heat but instead absorbs the heat from outdoors and transfers it indoors in winter. This process is reversed in summer as the heat is released outdoors.

It uses a gaseous substance called refrigerant to transfer heat. In heating mode, the pump extracts warmth from the outside air, ground, or water and transfers it indoors. In cooling mode, the process reverses, expelling the heat outside.

Related: Heat Pump for Cooling: Do Heat Pumps Actually Work in Summer Season?

1. Heat Pump Is in Defrost Mode

If you’re wondering why your heat pump is blowing cold air, then the most likely reason may be that your heat pump has entered defrost mode. This happens when the temperature outside dips too low, and your heat pump’s outdoor coils may freeze. During this process, warm air is directed toward the outdoor unit to melt any accumulated ice or frost. This means that, instead of heating your home, it is working to melt the ice. You can tell if your heat pump is in this mode by checking your outdoor unit for any signs of an icy surface.

Once all the ice has melted off the system, your heat pump will go back to warming your home like normal.

Related: Air Conditioner Freezing Up? Explore the Causes of AC Freezing and What You Can Do

2. Dirty Air Filters

Air filters are a crucial part of your heat pump system. They remove dust, debris, and pollutants from the air and help circulate clean air in your home.

If your heat pump isn’t working properly, then it is likely the filters are dirty. Dirty filters can drastically reduce indoor air quality. You will also experience reduced airflow in your home as the air struggles to pass through the clogged filters. This also negatively impacts your HVAC system. When a dirty filter impedes that airflow, your heat pump will struggle to maintain your ideal home temperature. This increases the strain on the unit and also results in high electricity bills.

The solution is quite straightforward – clean your AC filters regularly. You should wash the filters every two weeks and replace them every 3-4 months. If you have indoor pets, you may need to increase the frequency of filter cleaning.

The cleaning process is simple, and you can even do it yourself. Refer to your heat pump’s manual and remove the filters. Then, use a vacuum cleaner or an air hose to clean them. If you have washable filters, gently wash them with a mild soap solution. Let them dry completely before putting them back.

Tip: If you have a mini-split heat pump, you can use a smart mini-split thermostat to monitor the air filter status. It will send you reminders when it’s time to clean the filters.

3. Inaccurate Thermostat

If you can’t find any issue with your heat pump but it keeps blowing cold air in heat mode, try checking your thermostat settings. You might have accidentally set it to ‘cool’ mode. Change the settings, and your heat pump will be blowing warm air in no time.

Related: Thermostat Not Working? 13 Reasons Why & Troubleshooting Tips

4. Refrigerant Leakage

Refrigerant, commonly known as a coolant or Freon, is a chemical compound that absorbs heat from the outside air, which is then circulated in your home. This process is reversed in summer when the refrigerant absorbs heat from the indoor air to expel it outdoors.

The refrigerant in your heat pump keeps on circulating in a closed loop and is not depleted over time. However, some issues in your unit can cause it to leak. Age-related wear and tear, small pinhole leaks in the coils, and physical damage to the outdoor unit can result in refrigerant leakage. Due to low refrigerant levels, you may find your heat pump is blowing cold air in heat mode.

To recharge the refrigerant and fix the leakage, it’s best to contact a technician, as Freon is a dangerous chemical. It is an odorless, colorless gas that can cause headaches and dizziness and, if left ignored, even lead to refrigerant poisoning.

5. The Air Feels Cold Due to Temperature Difference

If you recently switched to a heat pump and were previously using a furnace, you will notice a difference in air temperature. The reason is that the heat pump produces air in the 85-92 F temperature range. On the other hand, a furnace blows air between 130-140 F. While the heat pump’s temperature range is lower than a furnace’s, it can perfectly warm up your space but takes a bit longer.

Related: Heat Pump vs. Furnace: The Best Way to Heat Your Home

Another reason can be that you perceive the air coming out of the heat pumps as cold because it’s less warm than your average body temperature, which is 98.6 F.

To check out whether the air is actually cold or you are just feeling it, follow these steps:

• Make sure the heat pump is on the heat setting. Sometimes, the symbols can get confusing, so refer to your manual to make sure the correct mode is selected.
• An infrared thermostat measures the air temperature. Take readings every 30 minutes. The temperature should become stable after an hour. If it doesn’t, call a technician to find out what’s wrong with the unit.
• If you don’t have an infrared thermometer, then you can wait for some time to see if your house warms up. If it does, then the unit is performing its job.

6. Dirty or Blocked Outdoor Unit

Heat pumps take in heat from the outdoor air and circulate it indoors. However, if the outdoor unit is clogged with debris, it will struggle to absorb heat.

Go outside where your heat pump is installed. Examine it in detail and check if it looks dirty. If it’s surrounded by shrubs, leaves, or twigs that have gotten stuck inside the unit, it’s time to clean it. Trim the vegetation surrounding the unit and remove all the visible dirt. Regular maintenance of your outdoor unit ensures that it runs efficiently and helps avoid costly repairs.

7. Dirty Coils

Heat pumps rely on refrigerants in the coils to absorb heat from the air, but dirt builds up on the coils, reducing their efficiency. Outdoor coils, which are exposed to weather, often collect debris like leaves, twigs, and dirt. This buildup can block airflow and hinder the system’s ability to function properly. Keeping the area around the unit clear and the coils clean ensures better heat absorption and overall system performance.

To clean your coils, first turn off the power and the circuit breaker, open the outdoor panel to locate the coil fins, and use a brush or vacuum to remove dust or debris.

8. Fan Set to Auto

Sometimes, there’s nothing wrong with your unit; it’s just an incorrect setting that is causing it to blow cold air. For example, if your fan setting is ‘on’ instead of ‘auto,’ this can cause your heat pump to blow air even when it isn’t heating, making it feel like the heat pump is blowing cold air on heat mode.

The solution is to set your fan to ‘auto’ so it only blows hot air.

9. Lack of Maintenance

One of the most common reasons a heat pump might be blowing cold air in heat mode is a lack of HVAC maintenance. Over time, dirt and debris can accumulate in the unit, impacting the heat transfer process and reducing the heat pump’s efficiency.

Regular maintenance is key to efficient operation. This includes cleaning the outdoor unit and scheduling an annual HVAC tune-up with a professional. Basic HVAC maintenance cost for your heat pump is between $80 and $150 annually. In addition to improving the performance of your system, it can also lead to cost savings. A well-maintained heat pump consumes up to 25% less energy.

10. Faulty Reversing Valve

The reversing valve is an integral component of your heat pump system. Its job is to switch the refrigerant flow, which means going from cooling to heating and vice versa. Damage or failure of the reversing valve can prevent your heat pump from switching between the two modes correctly. You will notice that your heat pump is blowing cold air even when you have set it to heat.

You will have to call an HVAC technician to troubleshoot the reversing valve and make repairs or replacements where necessary. Ensuring that your reversing valve is working properly can help ensure your heat pump performs optimally in both warm and cold months.

11. Your Heat Pump Has Run Its Course

A heat pump’s lifespan is about 10-15 years, but this can vary depending on the type of heat pump, the level of maintenance, and the environment.

As it moves into the later years of its life, it may become less efficient as parts slowly start to wear out or break down. One of the main signs you will notice is diminished airflow or the heat pump not blowing hot air at all. Other symptoms are that your unit struggles to maintain the set temperature, draws more power than usual, and requires frequent repairs.

When your unit is nearing the end of its life, the best course of action is to consult an HVAC professional and evaluate the cost of repairs. If it’s 50% of the original price, it’s better to replace it with an energy-efficient model.

12. Snow/Ice Buildup

In areas where it is too cold during the colder months, snow and ice buildup on your outdoor unit may cause the heat pump to blow cold air in winter. When your heat pump is turned on, it will melt the ice; however, when it reheats, it will expand and may bend your coil fins.

To prevent snow and ice buildup, you can sweep away the snow/ice with a shovel, or alternatively, you can build a cover around your outdoor unit, like a fence. If you want to follow the route of building a fence, make sure that there is enough distance between the unit and the fence structure to prevent any fire hazards.

In Conclusion

If your heat pump is blowing cold air, there could be many reasons for it, including an activated defrost mode or dirty air filters that prevent warm air from flowing properly. The outdoor unit can also be dirty or blocked, so clear any debris away from it. Additionally, don’t forget to double-check that your thermostat settings are correct. The best way to avoid heat pump airflow issues is to keep up with HVAC preventative maintenance.