Heat Pump Freezing Up? Here Are 9 Things to Check

Your heat pump is freezing up, and you don’t know why. In most cases, it’ll fix itself because there’s a defroster in the system. But if it’s been longer than four hours and your heat pump still looks like an icicle, it’s time to determine what’s wrong or hire a local heat pump professional to address the issue.

1. Air Filter Issues

When it comes to figuring out what causes a heat pump to freeze up, it’s easy to imagine the worst-case scenario. However, the first thing you should check is fairly straightforward, regardless of the type of heat pump you have: your air filter.

In an ideal world, you’ll clean or replace your air filter monthly. But if you missed the memo or if you’ve simply been too busy to remember, this is the first thing you should look into.

When an air filter is too clogged and dirty, it blocks the proper airflow that allows your heat pump to work as it should. In fact, the warm air that your heat pump wants to pull from the air isn’t able to enter the system. This can lead to a heat pump freezing up in winter. If your air filter is dirty, simply clean it if it’s reusable or install a brand new one if it’s disposable.

2. Low Refrigerant Levels

Maybe you’re wondering—why is my heat pump freezing up in summer? It’s definitely the opposite of what you’d expect in hot weather. The culprit might be low refrigerant levels, and this can happen anytime throughout the year.

Your heat pump refrigerant level should be stable without extra maintenance. However, it can get low if there’s a leak somewhere. Common times when refrigerant may leak are when fittings fail, there’s a bad solder joint, or a valve fails.

When the refrigerant levels are low, your heat pump has a hard time pulling in the hot air from outside. This can lead to a frozen-over unit. To fix this, you’ll need to fix the leak and replace the lost refrigerant.

3. Blower Motor Failure

The blower motor in your heat pump circulates the air inside the system. If the blower motor goes out or starts to malfunction, then your unit isn’t getting proper airflow. This can lead to more moisture building up in the heat pump than normal. And if the temperatures plunge outside, this moisture can turn into ice.

If a blower motor failure is the culprit, you’ll need to get a new one installed. Hire a heat pump installer near you for help.

4. Clogged Blower Motor Fan Blades

Over time, debris and dirt can build up on your blower motor fan blades. A heat pump fan that’s not spinning can lower the airflow in your heat pump and lead to unusually high levels of moisture, which can then cause the unit to freeze over.

5. Reversing Valve Failure

If your reversing valve fails or gets stuck in your heat pump, then your system is not switching properly between the cooling and heating settings. This can cause frozen-over heat pumps and high electric bills.

The best-case scenario is that your reversing valve is stuck. You may be able to simply fix it by tapping on the valve body. Otherwise, you’ll need to replace the valve if there’s physical or mechanical damage.

6. Dirty Evaporator Coils

Dirty evaporator coils can lead to freezing because dirty coils don’t absorb or transfer heat the way they should. Luckily, this is a common heat pump issue that many people can troubleshoot on their own. You can clean your coils by using a condenser cleaning solution or with soapy water. And for future maintenance, you should plan on cleaning your coils regularly, at least twice a year.

7. Defrost Sensor Failure

Your heat pump has a defrost setting that’ll kick in when it needs to. However, if the sensor is damaged or malfunctioning, then the defrost setting doesn’t come on, leading to a frozen heat pump. You’ll need to fix or replace the sensor.

8. Blocked Drainage Path 

When your heat pump was newly installed on your concrete slab, the pump was properly leveled by the installer. But over time, the concrete slab can settle. If this happens, then the drainage path may become blocked, which can cause ice buildup. To fix this, you’ll need to get a tech to re-level your heat pump.

9. Leaky Gutters

Also, when you’re trying to figure out how to fix your heat pump freezing up in winter, you should check your gutters. It’s possible that water is dripping down from your gutters onto your heat pump. In freezing weather, this will quickly lead to ice buildup on your unit. If this is your issue, you need to fix your gutters so the runoff doesn’t fall onto your unit.

Signs of Frozen Heat Pump 

These signs are reliable indicators that your heat pump is freezing up and needs repair or replacement. 

• Ice on outdoor unit 

• Strange noises 

• Reduced heating efficiency 

• Unusual odors 

• Faulty thermostat readings

• Increased energy bills

• System shut-off or error codes

How to Prevent Your Heat Pump from Freezing Up

The best way to prevent your heat pump from freezing is to perform regular maintenance on it. Whether you conduct the inspection yourself or hire a heat pump professional to do it, it helps to consult a maintenance checklist to make sure all the necessary steps are covered. In between inspections, be sure to adhere to the following guidelines: 

Clear the Area Outside

For your heat pump to work properly, you need to keep it cleared off. If there are any leaves or debris on or around the unit, clean them off. If you had a big snowfall, then you should clear that off, too, by watering it down with a hose. Keep in mind that your heat pump needs 2 to 3 feet of clearance, so you might need to trim back overgrown bushes and hedges.

Clear the Area Inside

After you clear off your heat pump unit outside, go inside and check all of the air vents and registers. These should be cleared off. If there are items blocking the vents or registers, like furniture or piles of clothing, you need to move them. Blocked airflow indoors can cause your heat pumps to freeze up.