What Causes a Heat Pump to Go Bad? Common Failures and How to Avoid Them

Heat pumps are one of the most efficient ways to heat and cool your home, but they don’t last forever. When your heat pump stops working, it’s not always a simple fix. Most of the time, it’s the result of something that’s been slowly going wrong for months-or even years. You might think your heat pump just died out of nowhere, but the truth is, it usually gave you warning signs long before it failed completely.

Dirty Air Filters Are the #1 Killer

It sounds simple, but a clogged air filter is the most common reason heat pumps break down. When dust and debris block airflow, the system has to work harder. That extra strain heats up the compressor, the most expensive part of the unit. Over time, that heat damages the motor windings and seals. A compressor that runs too hot will eventually lock up and stop working entirely.

Most manufacturers recommend changing the filter every 1 to 3 months. But if you have pets, live in a dusty area, or run your heat pump year-round, you might need to change it every month. Check it once a month. If it’s gray or you can’t see light through it, replace it. No exceptions.

Refrigerant Leaks Don’t Fix Themselves

Heat pumps use refrigerant to move heat in and out of your home. It’s not fuel-it’s a closed-loop fluid. If your heat pump is low on refrigerant, it’s not because it ran out. It’s because there’s a leak. And leaks get worse over time.

A system with low refrigerant will struggle to heat or cool. You might notice ice forming on the outdoor unit, or your home takes forever to reach the temperature you set. The compressor then runs longer and hotter, trying to make up for the lost cooling power. That’s how you end up with a burnt-out compressor.

Adding more refrigerant without fixing the leak is like putting gas in a car with a hole in the tank. It’s a waste of money. A trained technician should find the leak with a pressure test and dye, then repair the copper line or valve before recharging the system.

Bad Thermostats and Wiring Issues

Not every heat pump failure is mechanical. Sometimes the problem is the thermostat. Older models, especially those with dial settings or non-programmable units, can drift out of calibration. If your thermostat thinks the house is 72°F when it’s really 65°F, your heat pump won’t turn on when it should.

Wiring is another silent killer. Rodents chew through wires. Moisture corrodes connections. Loose terminals cause arcing and overheating. If your heat pump turns on and off randomly, or doesn’t respond to the thermostat at all, check the wiring. Look for frayed insulation, burnt spots, or loose screws at the terminal block. Even a single loose wire can cause the system to shut down for safety.

Outdoor Unit Problems: Dirt, Ice, and Debris

Your heat pump’s outdoor unit is exposed to everything: leaves, snow, grass clippings, bird nests, and even raccoons. If the coils are clogged with dirt or covered in ice, the system can’t exchange heat properly.

In winter, ice buildup is normal during defrost cycles-but if ice stays on the unit for hours, something’s wrong. A dirty coil, low refrigerant, or faulty defrost control board can prevent the system from melting ice properly. That ice blocks airflow, forcing the compressor to work harder.

Keep the area around the outdoor unit clear. Trim bushes at least 2 feet away. Clean the coils once a year with a garden hose (turn off power first). Don’t use a pressure washer-it bends the delicate fins. A soft brush and water are all you need.

Old Age and Lack of Maintenance

Most heat pumps last 10 to 15 years. After 12 years, parts start to wear out faster. Bearings in the fan motor get noisy. Capacitors swell and fail. Control boards corrode. The system becomes less efficient, uses more electricity, and breaks down more often.

If your heat pump is over 10 years old and you’ve never had it serviced, you’re playing Russian roulette. A professional tune-up includes checking refrigerant levels, cleaning coils, testing electrical connections, lubricating moving parts, and inspecting the defrost cycle. These checks cost $100-$150 but can add 3-5 years to your unit’s life.

Some homeowners wait until the heat pump dies to replace it. That’s a mistake. If your system is 12+ years old and needs a $1,200 repair, it’s probably cheaper to replace it. New models are 30-50% more efficient and come with smart features that save money long-term.

Electrical Problems: Capacitors and Compressors

Capacitors are small, cylindrical parts that help start the fan and compressor motors. They’re like the spark plug for your heat pump’s engine. When they fail, the motor won’t turn on-or it might hum but not spin.

You can often tell a bad capacitor by its shape. If it’s bulging, leaking oil, or cracked, it’s dead. Replacing one costs $50-$150, but if you ignore it, the compressor can burn out. And replacing a compressor? That’s $1,500-$3,000.

Compressors fail for three main reasons: overheating, low refrigerant, or electrical surges. A power surge from a storm or faulty wiring can fry the windings inside the compressor. That’s why a surge protector for your heat pump is a smart investment-especially if you live in an area with frequent lightning or unstable power.

What You Can Do to Prevent Failure

Here’s a simple checklist to keep your heat pump running longer:

1. Change the air filter every 1-3 months (monthly if you have pets).
2. Clear debris from around the outdoor unit every fall and spring.
3. Have a professional inspect and clean the coils once a year.
4. Check the thermostat settings and replace batteries annually.
5. Listen for strange noises-squealing, grinding, or loud buzzing.
6. Watch for ice on the outdoor unit in winter.
7. Upgrade to a programmable or smart thermostat if you still have an old dial model.

These steps don’t cost much, but they prevent 80% of major failures. Most people think heat pumps are maintenance-free. They’re not. They’re like your car-you wouldn’t skip oil changes for 10 years. Don’t do that to your heat pump either.

When to Replace Instead of Repair

Here’s a quick rule: if the repair cost is more than half the price of a new unit, replace it. That’s the 50% rule. If your heat pump is 10+ years old and needs a $1,000 compressor replacement, a new system costing $3,000-$5,000 might be the better choice.

New heat pumps have higher SEER ratings (18-26 vs. 10-14 on older units). That means lower electric bills. They also work better in cold weather, have quieter operation, and come with smart diagnostics. Some utility companies even offer rebates up to $1,000 for upgrading to an efficient model.

Waiting too long to replace a failing heat pump can leave you without heat in winter or cooling in summer. Don’t wait for a complete breakdown. If your system is struggling, getting noisy, or costing more to fix than it saves, it’s time to think about replacement.