Is your Heat Pump not Heating? Find Tips on How to Repair it!

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How to troubleshoot a heat pump not heating your home during the cold weather.

While exploring topics about troubleshooting heat pumps, we have found that common homeowners’ complaints regarding heat pumps during the wintertime are when the unit is not heating, not heating enough, not blowing warm air, cooling but not heating, or in general not performing as it should.

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Here we’ll talk about a heat pump not heating, including common causes and repair tips:

Note: It is a good idea to contact your local heat pump technician to tune up a device regularly and as recommended by the manufacturer.

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Issues with the thermostat

Before you start searching for answers, “why is my heat pump not heating,” check the simple things first, such as power supply, breaker, and thermostat settings.

Make sure that both indoor and outdoor units are in the “on” position and there is a power supply with no interruption. Also, make sure that the circuit breakers on the electric panel didn’t trip. Heat pumps use 220-240v breakers.

Incorrect thermostat settings are often found “guilty.” If your heat pump is operating, but you feel cool air blowing, your thermostat might be set to “cooling” or fan mode. Change it to heat mode and set the temperature to your liking.

A miscalibrated or broken thermostat can also affect normal heat pump operation.

Low refrigerant charge

The refrigerant is the bloodstream of the heat pumps and air conditioners. It is used to transfer heat from one place to another, heating space in the wintertime and cooling in the summer. In wintertime, a heat pump would extract heat from the outside and move it inside your home, increasing the air temperature and heating the space.

Since the refrigerant plays an important role in heating and cooling, it must be efficient and fully charged.

If you find your heat pump not heating your home as it used to, and there is a drop in the heating output, your refrigerant content (charge) might be too low.

Since the refrigerant cycles inside the closed-loop and doesn’t get consumed over time, you might have a leaking or insufficient refrigerant charge from the start if the refrigerant level drops.

Some of the signs of the low refrigerant levels are:

  • Lower heat output
  • The gurgling sound inside the coils
  • Puddle of liquid under the coils (but not water/condensation)
  • Evaporation coils icing

If your heat pump is low on the refrigerant, it would be hard for the compressor to move the refrigerant through the system. There will be more stress on the components resulting in reduced performance, efficiency, and heat absorption. It would shorten the heat pump’s life and increase the energy cost.

The heat pump compressor can also burn out due to the lack of lubrication oil leaked out with the refrigerant.

While you might think that filling a heat pump with refrigerant is easy, think twice. It is much better and safer for you and your family to contact a heat pump expert to deal with the problem.

Dirty air filter

Regular maintenance is the key to proper heat pump operation. Cleaning an air filter is one of the recommended steps to take and prevent issues like not heating or not heating enough.

Since a dirty air filter can block the airflow and prevent normal air circulation through the coils and heat exchange, make sure to clean it regularly.

Outdoor coils are dirty or blocked

An outside unit acts as an evaporator during the wintertime and heating season, absorbing heat from the air. Heated refrigerant then goes to the indoor unit (condenser coils), passing the heat to inside air, heating the space.

If the outside unit of the heat pump is dirty, covered with snow, leaves, branches, or any other debris, it will affect the proper airflow. Also, if you have plants around or any other objects on the unit or nearby, you might experience troubles.

To avoid issues such as no heating or low-performing heat pump, follow the manufacturer’s instructions to provide a minimum clearance around the outside unit and clean it regularly.

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Reversing valve failure

Heat pumps are designed to heat and cool when needed. They switch between these two modes changing the direction of the refrigerant. This is done by utilizing reversing valves, and based on the requirements, set the temperature on the thermostat and outside temperature, the heat pump would either heat or cool. If the reversing valve is stuck in the cool mode, your home may never heat up.

The recommendation is to contact a professional technician to fix or replace a reversing valve.

Cold weather and frozen heat pump

During the extreme cold weather and snowy days, your heat pump can get covered with a heavy coat of ice and a thick sheet of snow. In both situations, there will be no heat transfer between the air and refrigerant inside the coils. Or it will be significantly reduced.

If the unit is not defrosting to melt any accumulated frost and ice, your heat pump will work much harder than before, leading to low performance and element failure. Common reasons for defrosting issues are faulty relays, controls, and sensors. You would need an expert to fix this problem.

When the heat pump is low on the refrigerant, the evaporation cycle is incomplete, so the moisture condenses on the evaporator coils, and due to low temperature – it freezes. This also happens when water from leaky gutters is dripping on the unit.

Another reason for ice accumulation is when the outdoor fan is damaged or broken, affecting the heat release.

What you can do about ice or snow accumulations is to remove anything that is blocking the unit, but be careful when cleaning as the fan coils are very delicate and can be easily damaged.

Frozen coils can significantly decrease the heat transfer, and there will be not much heat coming from the indoor condenser coils. This can be serious when outdoor temperatures are extremely low, resulting in low heating performance.


A problem with the heat pump not heating and blowing cold air in the heat mode can often be prevented with regular maintenance and professional service. Some problems you can solve on your own (which is rare due to unit complexity), while others require professional assistance.

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