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Heat Pump Defrost Cycle Not Working? Time To Troubleshoot

Your heat pump’s defrost control board initiates defrost cycles to prevent ice buildup on your unit. If your heat pump defrost cycle isn’t working, the cold weather may take a toll on your system.

Check Your Defrost Control Board

When your heat pump defrost cycle stops working, you may notice ice buildup on your heat pump’s refrigerant lines and coils. Check your heat pump defrost control board before your unit turns a cold shoulder on the heat in your home.

How to check if your heat pump defrost cycle isn’t working

  • Like most homeowners, you are likely aware of what your normal utility bills looks like each month. Sudden increases are usually a sign that something is off. If your day to day thermostat settings are the same, and outdoor temperatures are average for the season, you may want to take a closer look at well your HVAC system is running.

    If your heat pump is malfunctioning in the winter months, it could potentially double or even triple your average electric bill. This is because the system will be using the "back up" system, known as auxiliary heat, to keep the house warm.

  • Your thermostat will likely give some indication that the auxiliary heat is on. Some thermostats have an indicator light while others have messages, such as "aux heat on". It's normal for the auxiliary heat to come on for short periods of time during defrost cycles and very cold weather to supplement the heat from the heat pump. However, if the auxiliary heat is on the majority of the time, that means that the heat pump has lost efficiency or may not be running at all.

  • Check the breaker that your heat pump is connected to. If it's sitting half way between "on" and "off", it's tripped. Move the switch fully into the "off" position, then flip it back on. Make sure to only do this once. If the breaker happens to trip again, that's a sign of a larger problem and should be invesigated by a technician.

  • When your heat pump is running normally, it should go through a defrost cycle about once an hour when the temperature dips below 40℉. Each cycle will last 4–6 minutes, which should be enough to melt all the ice.

    Check around your outdoor unit for signs of ice buildup. If you see ice forming on the refrigerant coil, around the fins on the condenser, or on the lines running to and from the outdoor unit, then the defrost cycle isn't working.

If your heat pump’s defrost cycle is working properly, consider other reasons why your heat pump is struggling.

What To Do If Your Heat Pump Defrost Cycle Isn’t Working?

Once you determine your heat pump defrost cycle isn’t working, consult an HVAC professional to come to inspect and repair the issue for you. You may need to replace your defrost control board to get your system back up and running.

Need a helping hand? One of our Remote Assist technicians can help you troubleshoot any issues with your heat pump to prevent it from giving your home the chills.

NOTE: This content is for informational purposes only, and HomeX and its affiliates disclaim all liability related to it. If you decide to perform any tasks based on this information, you assume all risks, including the risk of loss or damage to property or personal injury.

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