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Heat Pump Troubleshooting: 3 Common Problems and Solutions


heat pump troubleshooting

Heat Pump Troubleshooting Can Be Tricky

If your space has a heat pump system that provides both heating and cooling, it may seem like there are twice as many possible causes when something goes wrong. A heat pump system does operate somewhat differently than a traditional air-cooled air conditioner. So how do you begin heat pump troubleshooting? And are there heat pump repair issues you can fix yourself?

In some cases, there are issues you can prevent and problems you can solve on your own when you are aware of the heat pump troubleshooting steps. Here is a list of the most common problems we see with heat pumps, possible causes, and what to do next.

Heat Pump Troubleshooting Problem #1: ICING UP

Heat pump frozen in winter

During the cold winter months, your heat pump’s outside unit will sometimes be covered with a coating of frost on the sides, or even light ice. In the winter, heat pump icing up is often perfectly normal. Every so often, the unit will go into defrost mode to remove that frost.

However, if the top of the unit has a heavy coat of ice, the coils are encased in ice, or the entire unit is covered with a thick sheet of snow and ice, this indicates a problem. All that ice prevents the transfer of heat between the refrigerant and the outside air, and impedes the operation of the heat pump. If you don’t take care of it soon, you could damage the unit beyond repair. Ice in the coils can damage the sensitive fins, the fan blades, and eventually lead to compressor failure.

Heat pump troubleshooting tips for winter icing:

  • The unit is not defrosting. Under normal conditions, your heat pump periodically switches to air conditioning mode for a few minutes, which heats up the outdoor coils enough to melt any frost and light ice that has accumulated. If the unit is not defrosting, ice can build up in a hurry. Defrost issues can be caused by faulty relays, controls, or sensors. There could also be a problem with the reverse valve that switches the unit from heat to air conditioning mode.
  • Outdoor fan problem. The fan motor may be failing or completely dead. Or the fan itself could be damaged, which impedes the release of heat from the unit and causes ice to accumulate.
  • Low refrigerant. If your heat pump system has a slow leak of refrigerant, eventually the charge becomes so low that the system is not producing enough heat to melt the frost. If this is the case, you will probably also have issues with the unit reaching set temperature.
  • Outdoor unit is blocked. If piles of snow have accumulated around the outdoor unit, the impeded air flow can cause more icing.
  • Water is leaking onto the unit. Water constantly dripping on the unit from leaky gutters can gradually form a layer of ice on top.


  • Actually, let’s start with what you should NEVER do: use a hard or pointy object to try to chip away the ice! Those fan coils are very delicate and can easily be damaged. Instead, use water from a hose to melt the ice.
  • Remove and debris or snow that may be blocking the unit.
  • Check for leaking gutters that may be dripping water onto the unit, and repair them.
  • Call your HVAC service tech to troubleshoot defrost issues.

Heat pump frozen in summer

If your heat pump is freezing up in summer (on either the indoor or outdoor unit), you could have a refrigerant leak, clogged filter, or very dirty coils that are keeping heat from transferring as it should.

Heat pump troubleshooting tips for summer icing:
In this case you should turn the system off to prevent further damage, and contact your HVAC professional for assistance.
For more information about this problem, see this related article: AC Troubleshooting: FROZEN HVAC System? Don’t “Let it Go!”.

Heat Pump Troubleshooting Problem #2: RUNNING CONSTANTLY

Heat pump running constantly in summer

In the summer, your heat pump might run constantly when your unit is struggling to reach a low set temp during those triple-digit heat waves. But if it’s not very hot and your HVAC heat pump is not cooling, you probably need a service call.

Before you call for service, check the thermostat to make sure it’s set correctly.

Read this to learn more about the causes of this problem: AC Running Constantly? Ignore It And You’ll Regret It.

It’s also possible that you have not had your HVAC heat pump serviced for a long time. If that’s the case, dirty coils could be preventing the unit from releasing heat. Over time, the unit works less efficiently. And, the grime on the coils can can erode the metal and make holes that cause refrigerant leaks. Once that happens, the unit doesn’t cool efficiently and keeps running constantly. In this case, you might be able to restore proper function with a service visit.

Related article: Air Conditioning Maintenance Doesn’t Cost. It Pays.

Heat pump running constantly in winter

Before you call for service, make sure the heat pump isn’t accidentally set to a/c mode, and that the set temperature is correctly set at the thermostat.

You might notice your heat pump runs constantly in cold weather. That’s just how the heat pump is designed to work. Heat pumps do run longer and put out less heat as compared to a furnace. But if the temperature is above the mid 30’s and it’s still running all the time, you could have a service issue, such as leaking refrigerant, a frozen outdoor unit (as we mentioned in heat pump troubleshooting problem #1), or compressor problem.

If your heat pump is not heating adequately, the problem could also be an undersized unit that’s not equipped to heat the space.  Or you could have a poorly insulated space and too much heat is being lost. Another possibility is a dirty system that is running poorly because it hasn’t been maintained in a while. Your HVAC professional can help you sort it all out.

Heat Pump Troubleshooting Problem #3: BLOWING COLD IN HEAT MODE

First of all, just check and make sure your unit was not accidentally switched to a/c mode. Next, check your outdoor unit is not iced over (see Heat Pump Troubleshooting Problem #1).

If not, your system may have a valve problem, a refrigerant charge issue, or a compressor problem.

It’s also possible that your heat pump has not been serviced properly and needs cleaning and maintenance (see Heat Pump Troubleshooting Problem #2).

If your heat pump is experiencing repeated issues and just not performing to your needs, it may be time to think about either investing in a new system or finding a new service provider that can better meet your needs. Either way, we have some insightful guidelines that can help you make the right decisions:

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