Quick answer
Heat pumps stop heating when refrigerant pressure is low, the fan or compressor is not running, or the controller has lost its temperature sensor reading. Because a heat pump moves heat rather than generating it, a small refrigerant loss shows up as weak heating long before it shows up as no heating. Power tripping during load shedding and never being restored is the single most common cause of an apparently dead unit.
Common causes
- Low refrigerant gas from a slow leak in the circuit
- Compressor or fan motor failure
- Sensor or controller fault leaving the unit unable to read demand
- Power supply tripped, very often after a load-shedding cycle
- Airflow blocked across the evaporator by leaves, dust or a wall built too close to the unit
- Ambient temperature below the unit's operating range on a cold Highveld morning
What you can do now
- 1Check the breaker and isolator and restore power if it has tripped
- 2Listen for the fan and the compressor — fan only, or silence, both narrow the fault
- 3Clear leaves, dust and obstructions from the airflow path around the unit
- 4Photograph any controller error code before it resets
- 5Check whether it heats at midday but not at dawn, which points to ambient limits rather than failure
When to call a professional
Book within the week, and use a refrigeration-qualified technician — refrigerant work is not general plumbing and handling it requires the right registration and equipment. If the unit is short-cycling or icing up, treat it as urgent, because running a compressor in that state is what turns a gas top-up into a compressor replacement.
Typical cost in Johannesburg
Diagnostic R750 · Common repairs R1,800–R6,500
Indicative ranges only. We provide written, itemised quotes before any work.
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