5 Heat Pump Problems you Can Fix Yourself – Troubleshooting Tips for DIY-ers

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Heat pumps are complex devices and are often hard to repair unless you have proper training and know what to do.

In some cases, there are heat pump problems you can prevent and fix yourself. And this is especially important in the middle of winter when your heat pump is not heating or producing enough heat.

Here, we will talk about 5 common issues, possible causes, and how to troubleshoot them.

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Problem #1: Heat pump is not heating properly (or not heating enough)

If your heat pump is not heating properly, the unit is not producing enough heat, or there is not enough warm air going through the registers, you might want to check the basics first, as described in our DIY troubleshooting guide.

Check the thermostat settings. If your heat pump turns on and off when it reaches the temperature set on the thermostat, and is blowing warm air, the unit is working just fine. If you don't feel warm, you might have to increase the temperature. Make sure to set the temperature until you feel comfortable.

If you feel cool air blowing from the registers, your thermostat might be set to cooling instead of heating. Correct the settings and adjust the temperature to your liking.

A faulty thermostat might also be the reason why it feels colder than before. Dirt buildup or improper calibration might cause the thermostat to be off by a few degrees.

Dirty air filters. As the heat pump efficiency and performance depend on the proper airflow, any obstructions such as dirty or clogged ductwork or air filter can prevent or significantly reduce incoming air. Check your air filter located in the indoor unit, and clean if needed.

In some cases, such as heavy accumulation, you would have to replace the filter.

Otherwise, inspect the air filter regularly and replace it when recommended.

Leaky ductwork. Reduced or weak airflow followed by lower unit's efficiency are often indicators of leaky ductwork and heat loss.

Depending on the location, some air leakage can be identified by the homeowners, and some not. By simply putting your hand over the exposed ductwork seals and connections, you might find where the air leaks.

If it is hard to find the leak, such as when the ducts are hidden behind the walls, you might have to contact an HVAC technician.

The outside unit is blocked. The proper airflow is not only necessary through the indoor unit and ductwork, but the outdoor unit also. The airflow can often be reduced or even blocked due to dirt, debris, snow, and ice.

The solution for this problem is proper and regular maintenance, and cleaning (as recommended).

And, if you don't have technical and electrical knowledge or the right tools to fix the heat pump, our recommendation is to contact a professional.

Note that heat pumps are designed to produce a steady stream of warm air, not the strong bursts of hot air as found in the air forced heating systems. And it also takes longer to heat the room to the desired temperature.

Problem #2: Heat pump is running constantly

The reason why your heat pump is constantly running during hot summers is because the unit is undersized or not able to deal with the heat load.

If the temperatures are not extreme and the unit is still struggling to reach the set temperature, you might have an issue with the unit, and you probably need to contact a technician.

A heat pump running constantly in winter is often a regular occurrence, and it also happens if the unit is undersized and cannot keep up with the cooling load or accidentally set to cooling (A/C) mode.

Usually, when the temperature is above 30 degrees and the house is adequately insulated, the unit should operate in cycles, ON and OFF.

In order to prevent any accidental heat loss, check the walls and doors for any air leaks and keep them closed when the heat pump is working.

Note that if you don't protect your heat pump from the cold air impact, the unit will work longer and harder, increasing the operating costs and reducing its life.

In the case of a refrigerant leak or faulty valves, you might want to make a service call, but do not turn off your heat pump as it might trigger backup heating and increase your costs significantly.

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Problem #3: Odor coming from the heat pump and air ducts

What causes a heat pump to smell odd, and how to deal with the problem?

There are many reasons why your heat pump smells musty, like fish or burning, sulfur or rotten egg, and they often include dirty drain pans, clogged drain lines, dry traps, dead animals inside the ductwork, or close to the air intakes and air leaks. 

Related: How to remove bad smell from air ducts

If your heat pump smells musty, you might have an issue with mold growing on the wet evaporator coils or in the air ducts. People also identify this odor with a dirty sock or mildew smell and wet clothes.

This stinky odor often happens when a heat pump goes into defrost mode, or after heating, for a short time, the unit goes into cooling mode.

It is similar to a situation when running an AC in the car when air conditioning was not used for some time.

This problem is often only temporary and goes away when an indoor coil gets cooled and bacteria release its odor into the air. But keep in mind that if the operating temperature is suitable for the accelerated bacteria growth, the problem could worsen.

The solution for this problem is to clean the coils and air ducts using a special cleaner, in addition to regular maintenance and air filter replacement.

If there is a burnt wiring problem, overheated or failing motor, or melting plastic, you might notice a fishy or burning smell from your heat pump.

Dealing with the electricity is always risky, so it is recommended to contact a professional.

Smells like sulfur or rotten egg are often related to the natural process of decaying of the dead animal.

Problem #4: Heat pump fan is not running or spinning

The heat pump fan is designed to bring the air inside your home or move the heat to the outside. It works together with the air handler and should spin when the thermostat calls for heating/cooling.

In wintertime, the fan could sometimes run non-stop to provide requested comfort, and that is normal. Also, when it goes into defrost mode to melt the frost on the coils, the condenser fan will stop turning - and that is also normal.

But, there could be some fan issues as well, where some inner components can get damaged too, such as when the compressor overheats. Note that replacing a compressor is expensive.

There are several reasons why your heat pump fan is not working, and here are some of the most common ones:

Blocked fan. If you find your heat pump working, but a fan is not spinning, something might be clogging it. Don't be surprised if you find a stick, leaves, wire, rock, or even a critter blocking the fan blade from spinning. Before trying to dislodge the fan, you must turn off the power. And, remember, always use a tool or stick, never your hands.

If the fan is not blocked, give it a spin, and if that works, check your motor as it might be broken down. Situations like burnt-out windings or the bearing seized up, often happen due to the overload or lack of maintenance.

Even a dirty air filter can cause your heat pump's motor to work harder, causing a burning smell. Note that a fan motor is expensive and it requires professional assistance.

Also, you might have a problem with one of the weak, faulty, or shorted capacitors. As they can go bad over time, make sure to inspect and replace if needed.

If you are trying to replace any of the electrical elements yourself, make sure to handle and discharge them properly, to prevent injuries.

Get HELP from a local licensed HVAC professional today!

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Problem #5: Heat pump is running but not cooling (blowing cold air)

As summer temperatures start increasing, having a heat pump not blowing cold air is something you want to repair as soon as possible. Nobody likes waking up in the middle of the night drenched in sweat and having long sleepless nights.

There are several reasons why the heat pump is running but not cooling, and here are some that are safe for the DIY-ers:

Thermostat problems. Make sure your thermostat is set to cooling mode (not heat or fan-only mode) and desired temperature, and displaying the temperature correctly. In order to start cooling, the temperature must be below the home's current indoor temperature.

A faulty or miscalibrated thermostat can also be the reason why your heat pump is running but not cooling.

Airflow obstruction. Reduced airflow, dirty air filters, and outside coils are also to be blamed for poor or no cooling since the performance is significantly reduced. Due to blockage, your HVAC system can overheat and shut down, leaving your home without cooling.

Check the thermostat's fan settings. Always set your fan settings on the thermostat to AUTO mode so the fan can run only when cooling/heating is activated. Otherwise, if the thermostat fan is set to ON, the fan will run continuously even if there is no need for cooling.

Refrigerant flows incorrectly. If your heat pump is operating during heating mode with no problems but doesn't want to switch to cooling mode, you might have a problem with the reversing valve. It might be stuck, so it cannot reverse the direction of the refrigerant fluid. The unit may also be low on refrigerant.

Other obstructions. Check all the vents and registers, rugs, and furniture, as they might be blocking the room from getting adequate cooling.


It is no fun when your heat pump is not working, especially in the middle of winter.

Whether you have to deal with a small or big heat pump problem, we advise you to take it seriously as it can affect your quality of life and increase your energy bill. Small issues, as mentioned above, can be easily fixed by the handyman, while more complicated problems should be handled only by a professional.

We always recommend that homeowners get familiar with basics such as how the unit works or about common heat pump problems. The more you know about the unit, the easier it becomes to recognize the problem and fix it.

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