A heat pump that is not heating can have causes ranging from settings and airflow issues to controls, defrost, equipment, or electrical faults. The symptom alone is not enough to identify the repair — but a few safe checks can help narrow it down before calling a technician.
A heat pump that is not heating can have causes ranging from a simple thermostat setting or mode error, to a dirty air filter restricting airflow, to the system performing a normal defrost cycle. It can also indicate equipment problems such as a refrigerant issue, a failed component, or an electrical fault.
Because these causes range widely in severity and required response — from adjusting a setting yourself to requiring a licensed HVAC technician — the symptom alone ("not heating") is not enough to determine the cause. A systematic approach starting with the safest checks first is the right starting point.
If you have already checked the thermostat, filter, and outdoor unit and the system is still not heating, professional diagnosis is the appropriate next step. Do not attempt to reset a tripped breaker repeatedly or investigate electrical components yourself.
Before calling a technician, homeowners can safely check the following four items. These require no tools and no opening of electrical panels.
Confirm the thermostat is set to Heat — not Cool, Fan Only, or Off. A mode that was accidentally changed is a common cause of a system appearing to fail. If your thermostat has a "Maintain Heat" or "Schedule" setting, verify the active program is set to heat the space.
Confirm the thermostat setpoint (the target temperature) is set above the current room temperature. If the room is already at or above the setpoint, the system will not call for heat. Try raising the setpoint by 2–3°C and wait a few minutes to see if the system starts.
A severely clogged air filter restricts airflow through the system. When airflow drops below a threshold, the heat pump may shut itself down as a protective measure, resulting in no heating. Locate the filter in your air handler or return-air grille, inspect it, and replace it if it is visibly dirty and grey.
Visually inspect the outdoor unit (condenser). If it is completely buried in snow, heavily iced over, or has debris (leaves, ice) blocking the coil or fan, this can prevent operation. Do not chip or pry ice off the unit. If there is a light frost, this is normal — the system handles it with defrost cycles.
These are the most frequent causes a licensed technician will investigate when a heat pump is not producing heat.
The thermostat may be set to the wrong operating mode (Cool or Fan instead of Heat), have a setpoint below the current room temperature, or have a temporary hold or schedule override active. This is the first thing to rule out — it is also the most common cause of calls where the equipment itself is fine.
A dirty or blocked air filter, closed or obstructed supply or return vents, or a collapsed duct can reduce airflow enough to trigger safety shutdowns or dramatically reduce heat output. Without adequate airflow across the indoor coil, the refrigerant circuit cannot transfer heat effectively into the space.
During cold weather, ice can accumulate on the outdoor coil. The system periodically enters defrost mode — reversing the refrigerant cycle to clear ice. During defrost, the system temporarily stops delivering warm air (and may feel like it is blowing cool air). This is normal and lasts a few minutes. If defrost runs very frequently or the unit remains heavily iced, that is a separate issue.
Standard or older heat pumps can have reduced heating capacity at very low outdoor temperatures. If outdoor temperatures are unusually cold and the system is running but output seems low, the equipment may be operating near its design limit. Cold-climate heat pumps are designed to maintain output at lower temperatures.
A heat pump depends on the correct refrigerant charge to transfer heat. A low charge (from a leak or improper prior service) or a failed refrigerant component can significantly reduce or eliminate heating output. This requires licensed diagnosis — refrigerant work is regulated and cannot be a DIY repair.
A tripped circuit breaker, failed contactor, defective control board, or communication error between the thermostat and the heat pump can prevent the system from operating. Some of these faults will appear as error codes on a thermostat display. Electrical diagnosis should be performed by a licensed technician.
If none of the safe checks above resolve the heating issue, if the system has not heated properly through more than one cycle, or if you have any of the following situations, call for professional diagnosis:
The circuit breaker for the heat pump has tripped more than once. There is a burning smell coming from the air handler, outdoor unit, or registers. The thermostat display is showing an error code. The outdoor unit is making an unusual noise. The system is running continuously but not warming the space.
Do not reset a tripped breaker multiple times in an attempt to get the system running — repeated trips mean the breaker is protecting against a real fault. Do not attempt to open the electrical panel, access wiring, or add refrigerant yourself. A licensed HVAC technician has the equipment and certification to safely diagnose these issues.
Climax Energy provides heat pump diagnosis and repair across Metro Vancouver. Call (250) 201-2030 to schedule service, or see our heat pump repair page for more information.
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If the checks above do not restore heating, request professional heat pump diagnosis — our technicians serve Metro Vancouver.
Answers to the questions we hear most often about heat pumps that have stopped heating.