When to Repair Your Heat Pump Yourself and When to Call a Technician

Most heat pump repairs require a licensed HVAC technician—refrigerant leaks, compressor failures, and electrical work are dangerous and illegal for homeowners to handle. However, you can diagnose the problem yourself, reset the system, clean filters and coils, and clear blocked vents. This saves you a service call fee if the issue is straightforward, and it gives you real information to tell the technician if you do need one.

Start with the steps in this guide before you call. If your heat pump won't turn on, is making noise, or is blowing cold air in heating mode, you can often pinpoint the cause in under 20 minutes. The most common fixes—a tripped breaker, a clogged filter, or a frozen outdoor unit—cost nothing and take minutes to address.

Key Takeaways

  • Check your thermostat settings, circuit breaker, and air filter before assuming the heat pump is broken—these three things cause most service calls.
  • A frozen outdoor coil in winter is normal during defrost cycles, but ice that does not melt within 30 minutes means the defrost system is failing and you need a technician.
  • Clean or replace your air filter every 30 to 90 days depending on dust and pets; a clogged filter reduces heating and cooling by 15 percent or more.
  • If the heat pump is running but not heating, check that you are in heating mode, not cooling mode, and that the thermostat is set above the current room temperature.
  • Refrigerant leaks, compressor noise, and electrical problems require a licensed technician and cannot be safely repaired at home.

Check the Thermostat and Power Supply First

Before you look at the heat pump itself, verify that the thermostat is set correctly and the system has power. Set your thermostat to heating mode (not cooling or auto) and raise the temperature at least 2 degrees above the current room temperature. Wait 5 minutes—the heat pump may have a built-in delay before the fan starts. If nothing happens, move to the circuit breaker.

Go to your electrical panel and look for a breaker labeled "heat pump," "HVAC," or "air handler." If it is in the OFF position or in the middle (tripped), switch it fully OFF, wait 30 seconds, then switch it back ON. This resets the system. Return to the thermostat and try again. If the breaker trips when ready after you flip it back on, do not flip it again—this signals an electrical fault that requires a technician.

If the breaker is already ON and the heat pump still will not start, check whether your thermostat has a battery backup. Some digital thermostats have a small battery compartment on the back or side. If the display is dim or blank, replace the batteries (usually AA or AAA) and try again. A dead battery is one of the most overlooked reasons a heat pump will not respond to commands.

Inspect and Replace the Air Filter

A clogged air filter is the single most common cause of reduced heating and cooling. The filter sits in a slot in your air handler (usually in a basement, attic, or utility closet) or sometimes in a return air vent on a wall or ceiling. Locate it and slide it out. Hold it up to a light source. If you cannot see light through it, or if it looks gray or brown with dust, it needs to be replaced.

Write down the size printed on the frame—usually something like 16x25x1 or 20x20x4. Buy a replacement at any hardware store or online. They cost between $10 and $30 depending on size and type. Slide the old filter out, note the arrow printed on the frame (it points in the direction air flows), and slide the new filter in with the arrow pointing toward the furnace or air handler, away from the return air duct.

Replace the filter every 30 to 90 days. If you have pets, allergies, or a dusty home, check it monthly. A clean filter improves airflow, reduces strain on the compressor, and lowers your energy bill. Mark your calendar or set a phone reminder so you do not forget.

Clear Ice and Debris from the Outdoor Unit

In winter, the outdoor unit may develop frost or a thin layer of ice during normal operation. This is expected—the defrost cycle automatically melts it every 30 to 60 minutes. However, if ice is thick (more than a quarter-inch) or does not melt within 30 minutes of the defrost cycle starting, the defrost system is not working and you need a technician.

Check for visible debris around the outdoor unit: leaves, branches, snow, or dirt blocking the fins. Clear away anything within 2 feet of the unit. If snow has drifted against it, gently brush it away with a soft broom—do not use a pressure washer or sharp tools, which damage the aluminum fins. If the unit is surrounded by a fence or shrubs, make sure air can flow freely around all sides.

In summer, the outdoor coil can become clogged with pollen, dust, or grass clippings. If the unit is accessible and you see visible dirt on the fins, you can rinse it gently with a garden hose on low pressure. Spray from the inside out (from the center toward the edges) to push debris away from the coil. Do not spray hard enough to bend the fins. If the coil is heavily fouled or you are uncomfortable doing this, a technician can clean it professionally.

Listen for Unusual Noises and Identify What They Mean

Normal heat pump operation produces a steady hum from the compressor and a whooshing sound from the fan. Unusual noises often signal a specific problem. A loud grinding or squealing sound usually means a bearing is failing or a belt is slipping—this requires a technician. A rhythmic clicking or tapping during defrost is normal and stops when the cycle ends. A hissing sound suggests a refrigerant leak, which is dangerous and requires when ready professional service.

A rattling noise often comes from a loose panel, fan blade, or debris inside the unit. Check the outdoor unit for loose bolts or panels and tighten them with a wrench if you can access them safely. If the noise is coming from inside the house (from the air handler), do not open it yourself—the internal components are complex and you may damage them. Call a technician instead.

If the heat pump is making noise but still heating or cooling normally, write down what the noise sounds like and when it happens (during startup, continuously, during defrost). This information helps a technician diagnose the problem faster if you do end up calling one.

Troubleshoot When the Heat Pump Runs but Does Not Heat

If the outdoor unit is running (you can hear the compressor and see the fan spinning) but your home is not getting warm, start by confirming the thermostat is in heating mode, not cooling or auto. Some thermostats have a mode dial or buttons; others have a digital display. Set it explicitly to "heat" and raise the temperature setting 3 to 5 degrees above the current room temperature. Wait 10 minutes for the system to respond.

Next, check whether the auxiliary or emergency heat has kicked in. Many heat pumps have a backup electric heater that activates when outdoor temperatures drop below a certain point (usually 35°F to 40°F) or when the system cannot keep up. If you see an "aux heat" or "emergency heat" indicator on your thermostat, the heat pump is working but the backup heater is running instead. This is normal in very cold weather, though it uses more electricity. If the outdoor temperature is above 40°F and aux heat is still running, the heat pump may not be operating efficiently and a technician should inspect it.

If the system is in heating mode and the temperature is set correctly but you feel no warm air from the vents, check the fan setting on your thermostat. It should be set to "auto," not "off." If it is set to "off," the blower will not run even though the heat pump is heating. Switch it to "auto" and you should feel air within a minute or two.

Know When to Stop and Call a Professional

Do not attempt to repair refrigerant leaks, compressor problems, electrical connections, or the defrost control board yourself. Refrigerant is toxic and requires special certification to handle. The compressor is the most expensive component and improper work can destroy it. Electrical work on a heat pump can cause shock or fire. If you smell a chemical odor near the outdoor unit, see oil leaking from pipes, or notice the compressor is very hot to the touch, turn off the system and call a technician when ready.

If you have completed all the steps above—checked the thermostat, reset the breaker, replaced the filter, cleared debris, and listened for abnormal noise—and the heat pump still is not working, you have done the diagnostic work. Write down what you found: the thermostat settings, whether the breaker was tripped, the filter condition, any ice on the outdoor unit, and any unusual sounds. Give this information to the technician when you call. It will help them arrive prepared and may reduce the service call time.

Frequently Asked Questions

Why is my heat pump making a hissing sound?

Hissing usually indicates a refrigerant leak. This is not safe to ignore and requires a licensed technician to locate and repair the leak and recharge the system. Do not attempt to add refrigerant yourself—it requires special tools and certification.

Is it normal for the outdoor unit to be frosted over in winter?

Yes, frost is normal during heating mode. The defrost cycle automatically runs every 30 to 60 minutes and melts the ice. If ice remains thick after 30 minutes or the unit stays frozen solid, the defrost system is failing and you need a technician.

How often should I replace my air filter?

Replace it every 30 to 90 days depending on your home. Check it monthly if you have pets or allergies. A clogged filter reduces heating and cooling performance and strains the compressor, so replacing it on schedule saves money and extends the system's life.

Can I add refrigerant to my heat pump myself?

No. Refrigerant handling requires an EPA certification and special equipment. If your heat pump is low on refrigerant, it is leaking, and a technician must find and repair the leak before recharging. Adding refrigerant without fixing the leak is temporary and wastes money.

What should I do if the circuit breaker keeps tripping?

Do not keep flipping it back on. A repeatedly tripped breaker signals an electrical fault—either a short circuit in the heat pump or a problem with the breaker itself. Turn off the system and call a technician or a licensed electrician to diagnose the issue.