Why Is My Heat Pump Covered In Ice? A San Antonio Tech Answers

February 11, 2020
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Let’s make something clear right from the get-go: It’s perfectly normal for your outdoor heat pump to be covered in a small amount of frost during winter. Your heat pump actually comes equipped with a ‘defrost mode’, which periodically melts away any frost buildup on the unit.

What’s not normal is if that frost has covered your heat pump for a while (2 hours or so) and/or has since turned into ice.

If you notice that the frost has not melted and has since turned into ice, you may have one of the following complications:

  • A defrost control problem
  • A bad reversing valve
  • Low refrigerant

Continue reading to learn more about these complications and how they can lead to ice buildup on your outdoor heat pump.


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Some of the more common issues a defrost control can have include:

  • A bad defrost timer
  • A faulty thermostat
  • A damaged defrost display

Any of these issues can lead to the control not properly melting away the frost on your heat pump.

Solution: Have a professional diagnose the issue. A heat pump repair expert will typically start by checking the components listed above and should have all the proper tools to both repair and test your defrost control board (if that is in fact the origin of the problem).

The reversing valve controls which direction the refrigerant flows in your system. While in defrost mode, the reversing valve re-routes the directional flow of the refrigerant, that way the heat from the refrigerant can melt the ice on the outdoor unit.

However, if the reversing valve is broken or sticking, the heat pump won’t be able to reverse the flow of refrigerant in order to defrost itself. And over time the frost on your heat pump will build and eventually turn into an icey, expensive issue.

Solution: The technician you hire to fix your heat pump will have a close look at the reversing valve and ensure that it’s working properly and not sticking. If the valve is broken, they can either repair or completely replace it if necessary.

Your heat pump uses refrigerant to heat your home. If the refrigerant levels inside the system drop, the temperature and pressure of the refrigerant inside the heat pump drops as well.

Low refrigerant levels will cause frost, and eventually ice, to form on the refrigerant lines (and the ice will continue to build if no action is taken).

Now keep in mind that during proper operation, the refrigerant in your system should never run out. Refrigerant in a heat pump system runs in a closed loop and doesn’t get “used up” like gas in a car.

That being said, low refrigerant can only be caused by a leak somewhere in the refrigerant lines.

Solution: A heat pump technician will thoroughly inspect your system to pinpoint the exact location of the leak in order to properly repair it. Then, they’ll “recharge” the system to ensure proper refrigerant levels are restored.

Schedule an appointment now

Shafer has been serving the San Antonio community for well over 100 years and those who know us best know we love a good challenge. We can handle anything that’s thrown at us (especially heat pump repairs) and get it done right, for a fair price. We’ll have your heat pump repaired and running properly in no time!