Heat Pump Not Heating: Troubleshooting and Repair Cost
Work through these troubleshooting steps in order. The first four steps are free and take less than 10 minutes. If they do not resolve the problem, the later steps will help you identify what to tell the technician so they can diagnose the issue efficiently.
Step 1: Check the Thermostat Settings
This is the most common cause of a heat pump "not working," and it costs nothing to fix. Verify that the thermostat is set to Heat mode (not Cool, Auto, or Off). Make sure the set temperature is at least 2 degrees above the current room temperature. Confirm the fan setting is on Auto, not On. When the fan is set to On, it runs continuously even when the compressor is off, blowing unheated air through the registers, which feels cold.
If you have a programmable or smart thermostat, check the schedule. The thermostat may have automatically lowered the temperature based on a programmed setback schedule. Also check if anyone activated a "Vacation" or "Away" mode that reduces the set temperature.
Step 2: Check and Replace the Air Filter
A severely clogged air filter restricts airflow across the indoor coil, which can cause the coil to freeze and the system to shut down on a safety limit. Pull out the filter and hold it up to a light source. If you cannot see light through it, the filter is overdue for replacement.
Replace the filter with the correct size (printed on the old filter's frame) and restart the system. If the indoor coil was frozen, it may take 1 to 4 hours to thaw before the system resumes normal operation. Do not try to chip ice off the coil, as this can damage the delicate aluminum fins.
Step 3: Inspect the Outdoor Unit
Go outside and look at the outdoor unit. If it is completely encased in ice, the defrost cycle has failed, and the system cannot exchange heat with outdoor air. A thin layer of frost on the coil is normal in heating mode, but a solid block of ice is not. If the outdoor fan is not spinning, the fan motor or capacitor may have failed. If the unit is completely silent (no compressor hum, no fan), it may have lost power or the compressor may have failed.
Clear any snow, leaves, or debris that may be blocking airflow around the unit. The outdoor unit needs at least 24 inches of clearance on all sides to operate properly. In winter, make sure snow has not drifted against the unit or accumulated on top of it.
Step 4: Check the Circuit Breakers
Heat pumps use two separate circuit breakers, one for the outdoor unit and one for the indoor air handler. Both must be in the On position for the system to function. A tripped breaker may appear to be in the On position but actually be in a middle "tripped" position. Push the breaker firmly to the Off position, then back to On. If it trips again immediately, do not reset it a second time, as this indicates a short circuit or ground fault that requires professional repair.
Also check the disconnect switch near the outdoor unit. This is a small box on the wall next to the unit that contains a pullout fuse block or a switch. Make sure it is in the On position and that the fuses (if present) are intact.
Step 5: Reset the System
If the above checks did not resolve the issue, try a full system reset. Turn the thermostat to Off. Go to the electrical panel and turn off both the indoor and outdoor circuit breakers. Wait at least 5 minutes, which allows the control board's capacitors to fully discharge and any temporary fault codes to clear. Turn the breakers back on, then set the thermostat to Heat mode. Give the system 10 to 15 minutes to start up and begin producing heat.
If the system starts but shuts down again within 15 to 30 minutes, it is likely tripping on a safety limit such as high pressure, low pressure, or overtemperature. These safety shutdowns require professional diagnosis.
Step 6: Call a Technician
If none of the above steps restore heating, the problem involves a component failure that requires professional tools and expertise to diagnose and repair. Common causes at this stage include a stuck reversing valve, low refrigerant from a leak, a failed compressor, a defective defrost control board, or a failed capacitor or contactor.
When calling for service, tell the technician what you have already checked and describe any unusual sounds (grinding, clicking, hissing) or behaviors (ice on the outdoor unit, the system running but blowing cold air). This information helps them arrive prepared with the likely replacement parts.
Common Causes and Repair Costs
Once a technician diagnoses the issue, here are the most common causes and what they cost to fix.
Refrigerant leak and recharge: $300 to $1,500. The technician must locate the leak (using electronic leak detection or dye), repair it, and recharge the system with the correct amount of refrigerant. Small leaks at service valve connections are inexpensive to fix. Leaks in the evaporator or condenser coil may require coil replacement, which pushes the cost toward $1,500 to $2,500.
Reversing valve replacement: $400 to $1,200. The reversing valve switches the refrigerant flow between heating and cooling modes. A stuck valve traps the system in cooling mode, blowing cold air when heat is needed. The valve itself costs $100 to $300, with the remainder being labor for brazing (soldering) the new valve into the refrigerant lines.
Defrost control board: $200 to $600. A failed defrost board allows ice to build up on the outdoor coil until it blocks all airflow, preventing the system from exchanging heat. The board is an electronic component that plugs into the outdoor unit's control panel and is straightforward for a technician to replace.
Capacitor replacement: $150 to $400. The capacitor stores electrical energy to start the compressor and fan motors. A failed capacitor prevents the compressor from starting, even though the system receives power. This is one of the most common and least expensive repairs.
Compressor replacement: $1,500 to $3,000. This is the most expensive repair and may not be worth performing on a system older than 12 to 15 years. If the compressor is under warranty (typically 5 to 12 years depending on the manufacturer), you pay only for labor and refrigerant, which runs $500 to $1,200.
Outdoor fan motor: $300 to $700. The fan motor spins the blade that pulls air across the outdoor coil. A failed motor stops air circulation, causing the compressor to overheat and shut down on high-pressure safety.
When to Replace Instead of Repair
Replace the system rather than repair if the repair cost exceeds 50% of a new installation, the system is over 15 years old and needs a compressor or coil replacement, the system uses R-22 refrigerant (which is no longer manufactured and prohibitively expensive), or you have had three or more service calls in the past 12 months for different issues (indicating systemic age-related decline).
An emergency situation, such as a total heating failure during a cold snap, is the worst time to make a replacement decision because you are under pressure to restore heat quickly. If your system is over 12 years old, consider getting replacement quotes proactively so you can make a calm, informed decision when the time comes rather than scrambling during a crisis.
Start troubleshooting with the free checks: thermostat settings, air filter, outdoor unit condition, and circuit breakers. These resolve the issue roughly half the time. For component failures, common repairs range from $150 for a capacitor to $3,000 for a compressor. Replace rather than repair when the cost exceeds 50% of a new system or when the unit is over 15 years old.