Why Is My Heat Pump Not Heating? Tips for Troubleshooting & Fixes

There’s nothing quite as frustrating as coming home on a cold Ontario winter day, expecting warmth, only to be greeted by a blast of cold air from your heat pump. Is your heat pump not heating properly, don’t panic just yet. There are a number of reasons why this might be happening, and the good news is that some of them have easy fixes.

In this detailed guide, we’ll walk you through the most common reasons why your heat pump is not heating and what you can do about it. Whether it’s a thermostat issue, airflow restriction, frozen coils, or low refrigerant, we’ve got you covered. And if all else fails, LG Home Comfort is here to help!

How a Heat Pump Works (In Simple Terms) 

Before diving into troubleshooting, it’s helpful to understand how a heat pump operates. Unlike a gas furnace that generates heat, a heat pump transfers heat from the outside air into your home—even in cold temperatures. It works in reverse during the summer, providing cooling. 

Since a heat pump relies on extracting heat from outdoor air, its efficiency can decrease in extreme cold. That’s why many systems have a backup auxiliary heat source (like electric resistance heat or a gas furnace) for those particularly frigid Ontario nights. 

Now, let’s look at why your heat pump might not be keeping you warm. 

1. Thermostat Issues

Your thermostat is the brain of your HVAC system. If it’s not set correctly, your heat pump may not work as expected. 

Common Thermostat Problems: 

• Set to Cooling Mode? – It sounds obvious, but sometimes the thermostat is still in cooling mode. Double-check that it’s set to heat.

• Fan Set to “On”? – If your fan is set to “On” instead of “Auto,” it will run continuously—even when the heat pump isn’t actively heating. 

• Defrost Mode Activated? – Heat pumps sometimes switch to defrost mode to melt ice on the coils, temporarily blowing cool air. Give it a few minutes to cycle back. 

• Faulty Thermostat? – If none of the above fixes work, your thermostat might need recalibration or replacement. 

How to Fix It: 

✔️ Adjust the settings and wait a few minutes.  

✔️ If unresponsive, reset your thermostat or replace the batteries (if applicable).  

✔️ If still not working, consider upgrading to a smart thermostat for better control.

Read More: How Smart Thermostats Save Energy and Money

2. Restricted Airflow 

A heat pump needs proper airflow to transfer heat. If something is blocking airflow, your home may not warm up effectively. 

What Causes Poor Airflow? 

• Dirty Air Filters – Clogged filters block airflow and overwork your heat pump. 

• Blocked Outdoor Unit – Snow, ice, leaves, or debris can obstruct airflow. 

• Leaky Ducts – Air escaping from your ductwork reduces efficiency. 

How to Fix It: 

✔️ Check and replace dirty air filters (recommended changing is every 1-3 months).

✔️ Clear debris from the outdoor unit and trim nearby vegetation.

✔️ If you suspect leaky ducts, call an HVAC professional to seal them.

3. Low Refrigerant Levels

Refrigerant is what allows your heat pump to transfer heat. If your system is low on refrigerant, it can’t effectively extract heat from the outdoor air.

Signs of a Refrigerant Leak: 

🚨 Weak or no warm air coming from vents
🚨 Ice buildup on the outdoor unit
🚨 Hissing or bubbling sounds near the heat pump 

How to Fix It: 

✔️ Refrigerant isn’t a DIY fix. If you suspect a leak: Turn off the system to prevent further damage.
✔️ Call an HVAC professional to check for leaks and recharge the refrigerant.

4. Frozen Outdoor Unit

Some frost on your outdoor unit is normal. Heat pumps have a built-in defrost mode to melt ice. However, if the unit is completely frozen and stays that way, your system won’t be able to transfer heat.

What Causes Ice Buildup? 

• Restricted airflow (dirty coils, snow accumulation, or blocked vents) 

• Low refrigerant levels (causes the coil to freeze over) 

• Malfunctioning defrost mode (won’t remove ice buildup) 

How to Fix It: 

✔️ Turn off the system and let the ice melt naturally.
✔️ Clear any snow or debris around the outdoor unit.
✔️ If freezing persists, your defrost mode may not be working properly—call a technician.

5. Faulty Reversing Valve

The reversing valve allows your heat pump to switch between heating and cooling. If it gets stuck, your heat pump not heating issue could be caused by a mulfunctioning valveair.

How to Fix It: 

This is a job for a licensed HVAC technician. A faulty reversing valve may need repair or replacement.

6. Electrical Issues

Sometimes, the problem isn’t with the heat pump itself, but with its power supply. 

Check These First: 

🔌 Circuit Breakers – If the breaker for your heat pump has tripped, reset it.
🔌 Outdoor Power Switch – Ensure the disconnect switch near the outdoor unit is ON.
🔌 Indoor Power Switch – Some systems have a power switch that looks like a light switch. Make sure it’s ON. 

How to Fix It: 

✔️ If the breaker keeps tripping, this indicates an electrical issue—call a technician.

7. Auxiliary Heat Not Kicking In

Heat pumps use backup heating elements when temperatures drop below -20°C. If these fail, your home won’t stay warm. 

How to Fix It: 

✔️ Manually switch to Emergency Heat mode to see if it provides warmth. ✔️ If it doesn’t, your auxiliary heat strips may need repair or replacement.

When to Call an HVAC Pro in Ontario📞👨‍🔧

Some heat pump issues have simple fixes, but others require professional expertise. Call LG Home Comfort if:

✅ Your heat pump is not heating at all
✅ You hear strange noises like grinding or hissing
✅ The outdoor unit is frozen solid
✅ You suspect a refrigerant leak
✅ The heat pump keeps turning on and off frequently 

Our expert technicians will diagnose and fix the problem quickly, so you can stay warm and comfortable. 

Prevent Future Heat Pump Problems in Ontario🛠️

The best way to avoid breakdowns is with regular maintenance! Here’s how to keep your system running smoothly:

✔️ Change air filters every 1-3 months
✔️ Keep the outdoor unit free from snow and debris
✔️ Schedule professional maintenance twice a year (spring & fall)
✔️ Check for refrigerant leaks before extreme weather hits 

Read More: How to Save Money on Heating in Winter

Final Thoughts 

Your heat pump is designed to keep you warm—but when it stops working, it’s time to troubleshoot. Hopefully, this guide has helped you find the cause and solution to your heat pump woes. 

Still need help? LG Home Comfort is here for you! 📞Contact us today for expert heat pump repair and maintenance services.

Frequently Asked Questions

1. Why is my heat pump blowing cold air?

Your thermostat settings may be incorrect, the heat pump may be in defrost mode, or there could be low refrigerant levels. Check the settings and let defrost mode run before calling a technician.

2. How do I reset my heat pump if it’s not heating?

Turn off the heat pump at the thermostat and circuit breaker for 5 minutes, then turn it back on. If the issue persists, you may need professional HVAC repair.

3. Why is my heat pump running but not heating my house?

Possible causes include clogged air filters, blocked airflow, refrigerant leaks, or a faulty reversing valve. Inspect the filters and outdoor unit before calling a professional.

4. How do I know if my heat pump has low refrigerant?

Signs include weak heating, ice buildup on the outdoor unit, and hissing sounds. If you suspect a refrigerant leak, call an HVAC technician for an inspection.

5. Can a heat pump work in extreme cold weather?

Yes, but efficiency drops below -20°C. Many systems have auxiliary heating to support the heat pump in freezing temperatures.

6. What should I do if my heat pump is frozen?

Turn off the system and let it thaw. Check for airflow obstructions like snow or ice buildup. If it keeps freezing, the defrost mode may be faulty, requiring a professional repair.

7. How often should I replace my heat pump air filter?

Replace your air filter every 1-3 months to maintain airflow and efficiency. Dirty filters can cause poor heating and higher energy bills.

8. When should I call an HVAC professional for my heat pump?

If your heat pump isn’t heating, keeps short cycling, has ice buildup, makes unusual noises, or shows refrigerant leaks, call a licensed HVAC technician for diagnosis and repair.