Heat Pump Not Working? Common Causes and What to Do Next

When your heat pump, a device that moves heat into or out of your home using electricity and refrigerant. Also known as air source heat pump, it keeps your house warm in winter and cool in summer — but when it stops working, you’re left scrambling. Unlike a furnace that burns fuel, a heat pump moves heat around, which makes it efficient but also more sensitive to things like refrigerant levels, dirty filters, or frozen coils. If your heat pump is running but not heating, or not turning on at all, you’re not alone. Thousands of UK homeowners face this every winter, and most times, it’s not a full system failure.

A refrigerant leak, a loss of the fluid that carries heat inside the heat pump system is one of the top reasons a heat pump stops working properly. It’s not something you can top up yourself — it needs a certified technician. But before you call one, check the air filter, the part that traps dust and debris before air enters the system. A clogged filter cuts airflow, makes the system work harder, and can even cause the coils to freeze up. You can clean or replace it in under 10 minutes. Also, look at the thermostat, the control that tells your heat pump when to turn on or off. Is it set to heat? Is the battery dead? Is it accidentally on fan-only mode? These small things trip people up more than you’d think.

Another big one: ice on the outdoor unit. If you see a thick layer of frost or ice, your heat pump is in defrost mode — but if it’s stuck there, something’s wrong. It could be a faulty defrost control board, low refrigerant, or a bad fan motor. Don’t try to chip the ice off — that can damage the coils. Instead, turn the system off at the thermostat and let it thaw naturally. If it comes back on and works fine after, it was probably just a temporary glitch. If not, it’s time to call someone who knows heat pumps inside and out.

You’ll find posts below that walk you through exactly how to spot a malfunction, what to check before calling a repair tech, and how to tell if it’s worth fixing or if it’s time to replace. Some of these are simple fixes you can do yourself. Others will show you why certain problems need a pro — and how to avoid getting overcharged. Whether your heat pump is 3 years old or 12, these guides help you make smart, cost-effective choices without guessing.