12 Reasons Your Heat Pump Is Running Constantly (+ Fix)

As a heat pump owner, you might have been used to the normal noises the unit releases. Extra noises from the unit are its way of complaining about serious issues. So, when your ear perks up at the heat pump’s constant noise, it is time to examine the problem. 

The major reasons behind a heat pump constantly running are an oversized unit, dirty air filters, cold weather, and wrong thermostat settings. Buying the right unit size, changing the filters, and correcting the thermostat setting should troubleshoot the problem. Cold weather is beyond control.

Besides these, there are numerous other reasons behind a heat pump constantly running, and this guide will cover all the points in detail. So, stick to the article till the end to explore the reasons and troubleshooting steps. 

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How long should a heat pump run?

A heat pump is a unit that heats your room by transferring thermal energy from the outside with the help of a refrigeration cycle. 

Some heat pumps can also do the opposite by removing the heat from your room and cooling it.

A heat pump usually has 2 to 3 cycles per hour. 

The unit will run for 10 to 20 minutes during the ongoing cycle. 

It is enough for the heat pump to provide adequate energy throughout your house. 

When your heat pump gives you the desired temperature, it should shut off its heating cycle. 

Is it normal for the heat pump to run constantly?

A heat pump generally should not run continuously. 

Once it has reached its desired temperature, the heating cycle should shut down. 

If it doesn’t, the constant running signifies something is seriously wrong with the unit. 

However, it is common for the unit to keep running in the winter. 

Since the weather sometimes gets too cold, the heat pump will try to give you warm temperatures by running over time. 

It happens when the outside temperature goes beyond 30 to 40°F. 

So, do not worry if the unit constantly runs in the winter season. 

But, if the heat pump continually runs when the temperature is average or high, it indicates a problem.

You need to inspect it and call a professional if needed. 

Let’s learn the reasons behind the problem. 

1. Undersized heat pump size

Different house sizes will require different sizes of heat pumps. 

If the pump is smaller compared to what is needed by your house, the unit will not be able to give you sufficient warm air. 

As a result, the unit will keep running until it gives you the preferred temperature. 

In the winter, the unit will struggle more and end up overheating. 

You must buy the right heat pump size for your house. 

A suitable-sized heat pump will determine your house’s level of heat loss based on your house insulation and give the required temperature. 

What should I do?

If you have an undersized heat pump, you should exchange it and get the right size. 

Please do not go for an oversized heat pump, as it will quickly heat your house and cause short cycles. 

2. Wrong thermostat setting

Thermostat issues are numerous, for example:

  • Wrong thermostat setting
  • extreme temperature setting
  • Wire issues
  • Dead batteries 

Correct the fan setting

Generally, the thermostat setting for the heat pump should be set to HEAT or COOL, based on the outside temperature. 

The thermostat setting should be AUTO. 

It will signal the thermostat to turn off the heat pump once the heating cycle is over. 

The heat pump will constantly run without stopping if the fan is set to ON instead of AUTO. 

The solution is simple. Change the setting to AUTO. 

Set up a suitable temperature in the thermostat. 

Another problem with the thermostat is the temperature setting. 

Setting the thermostat to extreme temperatures will make your unit run continuously over time. 

For example, your heat pump will keep running and struggle to give you a temperature of around 77°F in the winter or 62°F in the summer. 

Check the thermostat and set the temperature to a suitable level, for example, between 65 and 75°F throughout the year. 

Check the wiring

The heat pump turns off when the thermostat sends a signal to the unit to deactivate the heating cycle. 

The unit will keep running if it does not receive the signal for shutting down. 

The reason could be frayed wires. 

The best solution is to isolate the circuit and remove the faceplate to check the thermostat wiring

If you find anything wrong, call an electrician to fix the wires. 

Replace the dead batteries.

Like the wire issues, a dead or low battery does not allow the thermostat to signal the heat pump to stop the cycle. 

As a result, the unit will keep running until it receives the signal from the thermostat. 

Thermostats without C-wires run by AA or AAA batteries. 

When they run low, the thermostat lacks the power to call off the heating system. 

Replace the batteries once a year to prevent the problem. 

3. Refrigerant leak

The refrigerant in the heat pump absorbs the heat from the surrounding air and releases cold air in the summer. 

It does the opposite in the winter with the help of the reversing valve. 

If the refrigerant liquid is leaking from the tube, you won’t be able to receive enough hot or cold air. 

So, the heat pump will constantly run and struggle to give you enough warm air without stopping the cycle. 

The leakage is caused due to rust, erosion, and cracks. 

What should I do?

Confirm the problem by looking around the unit for water droplets.

If you suspect refrigerant leakage in your heat pump, contact a professional HVAC team to replace the refrigerant tank.

Make sure that experts remove the tank first, replace it with a new one, and then refill it.

If they only refill the line, you will again face leakage issues. 

4. Dirty heat pump 

A clean heat pump will run more efficiently than the dirty one. 

Over time, dirt and debris can accumulate in the coils and air filters and restrict adequate airflow. 

Due to the clogged filters, the air cannot pass through and distribute around the house. 

As a result, the unit struggles to circulate the warm air and constantly runs until it provides you with the desired temperature. 

The airflow will also flow through the coils to circulate evenly all over the house. 

But dirt and debris will lower its capacity and reduce the unit’s efficiency. 

How do I clean the unit?

You must clean or change the air filters every 3 to 4 months. 

The changing time will increase or decrease based on the filter thickness. 

The thinner filters will need more frequent changing than the thicker ones. 

Check the filter every month to determine the dirt level. 

Some parts of the heat pump cannot be accessed without an expert’s help, for example, the evaporator coils. 

For such areas, you need a local HVAC team for help. 

5. Blocked air heat exchangers 

Since the heat pump is an essential part of the HVAC system, you should ensure its smooth functioning.

If you have an air source heat pump, enough air gets drawn across the heat exchanger to provide enough energy to the heat pump for heating the house. 

If the unit runs without ending the heating cycle, the reason would be blocked outdoor airflow. 

Over time, the heat exchangers will get clogged with leaves, dirt, and debris. 

As a result, the heat pump faces difficulty in working properly.

So, the unit will keep struggling and continue running until your house receives enough warm air. 

How to troubleshoot the problem?

You can check the heat exchanger yourself and remove the leaves and other dirt materials from it. 

The step should be a part of the annual maintenance and servicing. 

So, you do not have to do it if you have hired an HVAC team for the annual maintenance.

Besides regular annual maintenance, clean the surrounding area of the outdoor unit after yard work or strong weather. 

6. Frozen unit

In the winter, it is common for the heat pump’s outdoor unit to have ice buildup.

However, the unit has a default defrost cycle that helps melt the ice buildup from the heat pump. 

Due to the blockage and ice accumulation, it can block the airflow and make your unit run longer than it normally runs. 


There is no proper solution to this problem. 

You must wait for the temperature to become normal or let the defrost cycle do its job. 

You can melt the ice using the garden hose or warm water. 

Avoid scraping the unit with any sharp objects. 

7. Open or cracked doors and windows

If your house has many open windows and doors, your heat pump won’t be able to give you a comfortable temperature. 

In the winter, the cold air will enter your house through the open doors and windows, and the warm air will escape. 

As a result, your house will remain cold, no matter how hard it tries to give you a comfortable temperature. 

But, to give you the right temperature, the unit will work hard and keep running.

How to fix the problem?

When you turn on your unit, ensure the doors and windows are properly closed. 

If cracks or open bases exist, seal those areas. 

You can use weather stripping to seal the base of the windows and doors. 

The stripping will block the outside air and keep the dirt and debris from entering your house.

8. Poor or leaky insulation

Over time, the insulation of your house will weaken and become thin.

As a result, the cold outside air will enter your room easily.

Since the thin walls cannot stop the cold air from entering your house, the warm air provided by the heat pump won’t be sufficient. 

So, to keep your house warm and give the desired temperature, the unit will keep running.

The same happens if there are insulation leaks. 

The warm/cold air provided by the heat pump will escape through the leaks, and your house won’t get the desired temperature. 

So, the heat pump will constantly run to give you a comfortable temperature.

What should I do?

Make sure that your house is well-insulated. 

If you already insulated your house years ago, you should re-insulate. The insulation weakens over time. 

Call a professional to re-insulate your house and seal the leakages. 

9. The blower relay switch malfunctioned.

The blower relay switch controls the thermostat and heat pump communication. 

If the blower relay switch’s controller is malfunctioning, it will not let the thermostat communicate with the heat pump. 

As a result, the thermostat cannot signal the unit to stop, and the fan will keep running even if the heat pump is turned off. 


Try turning off the fan at the thermostat. 

If it does not work, you must replace the blower relay switch. 

Call a professional to replace the controller. 

10. Emergency heat activated

The thermostat has an emergency heat setting. 

Turning it on will bypass the primary heat pump source and turn on the auxiliary heat part to keep running until your house receives enough warm air. 

The problem will get coupled with a defrost cycle, making your unit run constantly. 


Check the thermostat setting. 

If you have activated the emergency heat or EM heat switch, reset your thermostat for normal operation. 

Call a professional if you cannot deal with it. 

11. Damaged compressor contactor

The contactor controls the electricity flow to the heat pump’s internal components. 

When the contactor is at fault, the heat pump cannot receive the electricity to give you the desired temperature. 

As a result, the unit will constantly run to give you warm air, but in vain. 

What to do with the contractor?

The contactor will need replacement. 

Call a professional for the replacement.

12. Stuck reversing valve

The heat pumps can be useful for both heating and cooling systems. 

It contains a reversing valve that switches between the heating and cooling systems whenever required. 

If the valve gets stuck, the heat pump will not reach the preferred temperature and keep running without any breaks. 

How can I fix the valve?

You need a professional to fix the problem. 

Check whether the vents’ air is hot or cold to confirm the problem.

If the air is cold but the thermostat setting is high, arrange for a professional inspection. 

Things to do before calling an HVAC expert

Before you call an expert, you should perform certain things when your heat pump constantly runs. 

All the problems won’t require an expert’s attention. Solving some of them yourself can save you time and money. 

  • Check the thermostat setting for your heat pump. It should be in the AUTO position, and the temperature must be average, neither too high nor too low. 
  • Check the outdoor unit, i.e., the heat exchanger. Consider cleaning the surrounding areas to clear the airflow blockage. 
  • Change the filters every 3 to 4 months. 

There are numerous reasons behind a heat pump running constantly.

Reasons like undersized units, dirty filters, wrong thermostat settings, drafty rooms, and blocked air heat exchangers are common and easy to fix. 

Others, like damaged contactors, stuck reversing valves, dirty coils, poor insulation, malfunctioning relay switch, and refrigerant leak, will need the HVAC’s attention. 

Regular annual maintenance and servicing of the unit can prevent the above issues and encourage the smooth functioning of the unit. 

What is the best temperature to set in the heat pump’s thermostat?

Extreme temperatures can keep the heat pump from stopping the cycles. So, the best temperature to set in the heat pump’s thermostat is 68°F. Lower or increase only 5 degrees if needed. 

Can I turn off the heat pump at night?

Generally, a heat pump should stay on at night to maintain an optimal temperature. Turning off the unit will break down or freeze if the temperature drops at night.

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Arthur Smith

Howdy! I am Arthur Smith, an electrical engineer who is extremely passionate about electronics. I have lived in different parts of the US and currently reside in Wisconsin. I am one of those rare children who knew what he wanted to study and do in life right from the start. I was a curious child who wanted to know how switches work and how the AC works, and I would always observe my dad whenever he would handle the wires and fix things around the house. I currently work as an electrical engineer at a reputed company and write for this blog. And I read loads of books or play video games in my free time.

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