Why Is My Heat Pump Blowing Hot Air In Cool Mode?

man suffering from high humidity at home due to heat pump blowing hot air

Heat pumps are extremely versatile. They offer comfort all year round as they can be used for home heating or cooling, depending on your needs and preferences. If it is too cold in the winter, the heat pump can warm your home. The same unit can also cool your home if it feels too hot. It can easily change modes and temperature settings. However, homeowners may find their heat pump, which is supposed to be cooling, is blowing hot air. Read on to find the reason behind a heat pump blowing hot air in cool mode.

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Why Does My Heat Pump Blow Hot Air in Cool Mode?

Heat pumps are durable, but they aren’t indestructible. A heat pump blowing humid and warm air during the cooling cycle commonly happens when heat pumps aren’t working as they should. Therefore, homeowners should learn the usual culprits behind this heat pump problem so that they can lessen the chances of it happening again. Getting familiar with the cause also means you can conduct basic troubleshooting before calling the experts to help perform advanced solutions. Here are seven of the usual suspects when you have this problem:

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Broken Reversing Valve On Heat Pump

heat pump refrigeration cycleThe versatility of a heat pump can be attributed to its reversing valve. The unit can either gather the heat from inside and release it outside or collect the heat outside to push it inside, depending on the setting. This valve leads the refrigerant flow to achieve the heat pump’s goal. A faulty reversing valve translates to the heat pump not working correctly. The solution typically includes replacing the valve and then topping up the system’s refrigerant. The expertise of trained HVAC technicians is needed to complete this complex process.

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Heat Pump Thermostat Problem

Many cases have the heat pumps behaving this way because of incorrectly programmed thermostats. The heat pump may have been set to have only the fan running, so it will blow warm air throughout your home. Check the settings to make sure it is set in cool mode. Otherwise, change the settings. Someone in your household may have changed it without your knowledge. It is also possible that the thermostat has low battery levels, so you need to replace it with new ones. Check the breakers as well because they may have tripped.

You may have a faulty thermostat if the problem persists. If so, you need a thermostat replacement. An old manual thermostat may be due for replacement so take this as a good opportunity to replace it. Basic programmable thermostats are available without you needing to spend a lot. However, if you are willing to pay a bit more, you can get better features.

Heat Pump Refrigerant Loss

image of an hvac contractor examining refrigerant levels of a heat pump unit

A heat pump doesn’t generate its own heat like a furnace does. Instead, a heat pump is equipped with refrigerant to absorb the heat from one place and release it to another. Insufficient refrigerant means the unit cannot do its job properly. There could be correct thermostat settings and a perfectly working reversing valve, but the system will still blow hot air even in cool mode. Not enough refrigerant can be because of a leak. A licensed technician can repair the leak and add refrigerant to your system right away.

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Clogged Heat Pump Air Filter

Air filters catch the dust and dirt in the air as it passes through the system. The debris settles on the filter surface while air passes unobstructed. This layer of dirt can become thick enough that it blocks the air from passing through. As a result, the heat pump struggles to operate. This is easy to resolve as all you need to do is clean the air filter to get rid of the blockage. It is better to replace the new filter to get a fresh start. Make sure to follow the manufacturer’s recommended frequency when it comes to cleaning or replacing the air filter. Remember that the environmental situation around your home may mean you need to change it more frequently.

Duct Leak In The Heat Pump

hvac ductwork repair

Ducts can degrade as time passes. Air can leak out if you have old ducts. This keeps the ducts from distributing conditioned air across your house. This leads to uneven cooling or heating, wherein some rooms feel warm while others feel cold. Finding the leaks can be hard. Contact an HVAC technician to help you resolve the issue. This way, you will have improved air distribution, reduced energy consumption, and lower energy bills. Repairing the ducts immediately means you enjoy long-term comfort and savings.

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Dirty Heat Pump Coil

The heat pump’s outside unit is susceptible to dirt because of its location. The amount of dust in the home’s surroundings should be kept in mind. Consider other factors like grass clippings, dried leaves, and pet hair as well. These can cause the heat pump coil to become dirty after some time. This can keep the unit from absorbing or expelling the heat via the coils properly. Therefore, it is a must to clean the coil regularly. You can hose the loose dirt off using low to medium pressure. Be careful about the hose settings, as high water pressure can damage the heat pump. Utilize a light brush to scrub off any stubborn spots.

Clean the indoor coils, too. These components may be harder to reach, so you can ask an HVAC technician to help you. Heat pump maintenance is relatively affordable, so you can get excellent results.

Frosted Indoor Coil On Heat Pump

ice on coil cooler of dirty heat pump

A frosted indoor coil can also cause heat pump malfunction. It may not seem absurd that a frosted coil can cause the unit to blow warm air while in cool mode. You will understand it better if you know how a heat pump works. The indoor coils can freeze when the water in the air condenses around these coils. This happens because of low temperatures. The ice stops the coil from absorbing heat, so the unit doesn’t work as it should. Repairing this issue means the system will have some downtime before setting the system in fan mode. This forces warm air through the coils, so they defrost quicker.

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Do I Repair or Replace the Heat Pump?

Homeowners may wonder when to continue repairing their heat pump or replace it entirely. Here are several considerations before deciding on what to do:

  • Heat Pump Warranty: Check if your heat pump is still under warranty. You can rely on the warranty for free labor fees and parts replacements if it is still ongoing. It is logical to keep the unit until the warranty becomes void.
  • Heat Pump Age: Heat pumps have a lifespan of a decade or more. Unfortunately, it will likely have wear and tear after reaching the 10-year mark. This means it requires repairs more often, and many homeowners do not want to deal with the hassle. Get a new one to have a reliable system.
  • Heat Pump Repair Vs. Replacement Costs: It is wise to calculate the cost of repair versus replacement to compare them. Make sure to add the repair bills from the past several years and an approximation of your future expenses. It may reveal that it is cheaper to buy a new heat pump than keeping your old one.



Heat pumps make your home comfortable all year round. It can blow cold air during the summer and hot air during the winter. Investigate the reason when your heat pump is in cool mode but blows hot air. The cause is likely one of those listed above. Contact an HVAC professional for immediate assistance.

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For first-rate heating and cooling services in Monmouth and Ocean Counties, New Jersey, call Lawes Company. We have the best professionally certified technicians who can offer superior HVAC services, such as heat pump maintenance, boiler repair, furnace replacements, and more. All our friendly techs have the skills, experience, and knowledge to conduct correct HVAC services on your system.

Our company offers highly affordable HVAC service rates in the area. Rest assured, our tune-up services can ensure you’ll have higher energy efficiency, better comfort, and reduced energy costs. If you need to repair or replace your HVAC system, we can recommend the most suitable one for your home within your budget. All our work is guaranteed because your satisfaction is our priority. Schedule a service appointment and call Lawes Company today. We offer free, in-home estimates.

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