Heat pump repair for both seasons of trouble
Heat pumps cool in summer and heat in winter with the same refrigerant circuit, so a fault can show up in either mode. Diagnosis starts by watching both.
- SystemsDucted, ductless and dual fuel
- Frequent faultsDefrost controls, reversing valves, sensors
- Also checkedAuxiliary heat strips and thermostat wiring
Why heat pump problems look different from AC problems
A heat pump is an air conditioner that can run in reverse. A reversing valve changes the direction of refrigerant flow so the outdoor coil either releases heat, in cooling mode, or absorbs it, in heating mode. That extra valve, plus the defrost system that keeps the outdoor coil from icing over in winter, adds components that a standard air conditioner does not have.
In winter, a heat pump pulls heat from cold outdoor air. On the coldest days, many ducted systems lean on auxiliary electric heat strips to help, and some homes pair the heat pump with a gas furnace in a dual fuel setup. When a heat pump struggles, the auxiliary heat can quietly take over, and the first sign of trouble may be an electric bill that jumps rather than a cold house.
Our technicians test the system in both heating and cooling modes where conditions allow, check the defrost cycle and verify the auxiliary heat and thermostat settings, so the repair addresses the actual cause.
Heat pump symptoms worth a service call
Some behavior that looks strange is normal for a heat pump. These signs are not.
Outdoor unit encased in ice
Light frost that clears during periodic defrost cycles is normal. A thick block of ice that stays points to a defrost control, sensor or airflow problem.
Blows cool air in heating mode
Air from a heat pump feels less hot than air from a furnace. Air that feels cold, though, can mean a stuck reversing valve or low refrigerant.
Stuck in one mode
A system that heats when it should cool, or will not switch at all, often has a reversing valve solenoid or thermostat wiring issue.
Emergency heat light stays on
If the thermostat shows auxiliary or emergency heat running constantly, the heat pump may not be carrying its share of the load.
Loud whoosh followed by silence
A brief whoosh during defrost is normal. Grinding, rattling or a unit that stops after a defrost cycle is not.
Winter electric bills spike
When the heat pump underperforms, electric resistance heat strips fill the gap at a much higher operating cost.
Our heat pump diagnostic approach
Review settings and history
Thermostat configuration, auxiliary heat staging and recent behavior are reviewed, because a wiring or setup error can mimic an equipment failure.
Airflow and coil inspection
Filters, blower operation and both coils are checked. Restricted airflow causes icing in winter and freezing indoors in summer.
Refrigerant and valve testing
Pressures and temperatures are measured, the reversing valve is tested for proper switching, and the metering devices are evaluated.
Defrost system check
The defrost board, sensors and timing are tested so the outdoor coil clears ice properly during cold, damp weather.
Repair and verify
After you approve the flat price, the repair is made and the system is verified in the mode it failed in, and in the other mode where possible.
Defrost cycles and auxiliary heat, the two winter wildcards
When outdoor temperatures hover near freezing and humidity is high, frost forms on the outdoor coil as the heat pump pulls heat from the air. To clear it, the system periodically switches into a brief cooling mode that warms the outdoor coil. During defrost you may see steam rising from the unit and hear a whoosh as the reversing valve shifts. If the defrost control, temperature sensor or valve fails, ice builds until it blocks airflow and the heat pump can no longer extract heat.
Auxiliary heat is designed to supplement the heat pump in very cold weather and to temper air during defrost. It is normal for it to run at times. It is not normal for it to carry the whole heating load. Thermostats that are not configured for heat pumps, outdoor temperature lockouts set incorrectly, or a heat pump that has actually failed can all leave the heat strips doing the work. Because resistance heat costs considerably more to run, fixing the underlying heat pump problem pays off quickly.
A quick owner check
Keep snow, leaves and ice from piling against the outdoor unit and make sure it sits high enough for meltwater to drain away. Never chip ice off the coil with tools, because the aluminum fins and copper tubing are easy to puncture.
How heat pump problems differ from air conditioner problems
A heat pump is an air conditioner that can run in reverse. In summer it moves heat from inside to outside, and in winter it pulls heat from outdoor air and moves it inside. That dual role adds components that a cooling-only system does not have, including a reversing valve, a defrost control and, in many cases, auxiliary electric heat strips or a backup furnace.
In winter, frost forming on the outdoor coil is normal. The heat pump periodically enters defrost mode, temporarily reversing to warm the coil and melt the frost. During defrost, you may see steam rising from the unit and hear the fan stop briefly. That is expected. A coil that stays encased in ice, however, points to a defrost control failure, a faulty sensor, low refrigerant or airflow problems.
Heat pumps deliver heat at lower air temperatures than a furnace, so the air from registers can feel cooler even when the system is working properly. If the heat pump cannot keep up in very cold weather, auxiliary heat should turn on. When auxiliary heat runs constantly in mild weather, it can indicate a heat pump problem and high electric bills.
Diagnosing a heat pump includes checking operation in both heating and cooling modes, testing the reversing valve and its solenoid, evaluating defrost operation, measuring refrigerant pressures and confirming thermostat settings. Many heat pump complaints come from thermostats configured incorrectly for the equipment, which is simple to correct once identified.
Heat pump mistakes homeowners make
Avoid these habits that reduce heat pump performance or cause damage.
Chipping ice off the outdoor coil
Using tools to remove ice can damage the delicate fins and refrigerant tubing. Persistent ice needs professional service instead.
Setting the thermostat back too far
Large temperature setbacks can trigger auxiliary heat during recovery, increasing electric use. Smaller setbacks or smart recovery settings work better.
Blocking the outdoor unit with snow
Snow drifts and roof runoff can bury the coil. Keep the unit clear and elevated so it can defrost and drain properly.
Using emergency heat routinely
Emergency heat bypasses the heat pump and runs only backup heat. It is meant for failures, not everyday comfort.
Ignoring unusual noises
Grinding, screeching or loud clicking may indicate motor, compressor or reversing valve problems that worsen if left unattended.
What determines a heat pump repair price
- The component involved
- Sensors, capacitors and defrost boards are moderate repairs. A reversing valve replacement involves refrigerant recovery, brazing and recharge.
- Refrigerant leaks
- Locating and repairing a leak, then recharging the system, is priced by the leak location and how much refrigerant is needed.
- System type
- Ductless and inverter-driven heat pumps use electronic components that vary by manufacturer and can cost more than standard parts.
- Warranty coverage
- Many heat pumps carry parts warranties that can reduce the cost of major components if the unit is registered and still covered.
Heat pump repair questions
Yes. During a defrost cycle, the outdoor coil warms up and melts frost, which can produce visible steam. It should last only a few minutes and then the unit returns to heating.
Heat pumps deliver air that is warm but not as hot as a furnace. The system runs longer, steadier cycles to reach the set temperature. Air that feels cold, however, suggests a problem.
Emergency heat can keep the home warm until a repair is made, but it is expensive to run. Use it as a temporary measure and schedule service promptly.
Modern cold-climate heat pumps are designed to keep heating at low outdoor temperatures. Older or standard models lose capacity as it gets colder and rely more on auxiliary heat.
Because it runs in both summer and winter, a heat pump benefits from service twice a year, before the cooling season and before the heating season.
Get the heat pump carrying its own load again
A technician will test your heat pump in both modes and quote a flat price for the repair.