Why is the heat pump not heating? The symptom narrows the next observation but does not identify a failed part. For the heat-pump system, first separate what the thermostat or normal controls request from what the indoor and outdoor equipment actually do. Note airflow, temperature change, timing, sound, odor, visible water or ice and whether the problem affects one room or the whole home, without opening a panel or reaching into equipment.
Design temperature, humidity, snow or coastal exposure, electricity rates, utility controls, and local equipment requirements shape performance expectations and repair decisions. Record thermostat mode and indicators, indoor airflow, outdoor-unit activity, visible ice, unusual noise, and whether supplemental heat appears, while staying clear of electrical and refrigerant components. Low-feeling supply air, a defrost interval, no airflow, and a home that steadily loses temperature are different conditions and do not independently prove loss of refrigerant or compressor failure. A heat-pump assessment can compare thermostat staging with reversing operation, airflow, outdoor and indoor coils, defrost controls, electrical components, supplemental heat, and measured system performance. When calling, provide the outdoor conditions and operating sequence and ask that heat-pump and backup-heat findings, proposed repairs, and final heating verification be itemized.