Heat Pump Not Cooling in Summer — Troubleshooting and Repair Guide
Published: July 15, 2026 — BC Wide Home Services Ltd, doing business as BC Wide Heating & Air Conditioning — Greater Vancouver, BC
First Checks Before Calling for Service
Verify your thermostat is set to Cool mode with the temperature set at least 3 degrees Celsius below the current room temperature. Check that the thermostat fan setting is on Auto, not On — the On setting runs the indoor blower continuously without cooling. Inspect the circuit breaker for the outdoor unit — toggling it fully OFF and back ON can reset a tripped breaker. Check the outdoor disconnect switch near the condenser — it should be in the ON position. Replace or clean the indoor air filter if dirty — restricted airflow is the most common cause of cooling problems. Clear debris, leaves, and vegetation within 2 feet of the outdoor unit.
Common Causes When the Heat Pump Runs but Does Not Cool
The reversing valve may be stuck in heating mode — if warm air comes from the vents when cooling is selected, the valve is not switching. A refrigerant leak causes gradual loss of cooling capacity — the air becomes cool, then warm, then the system stops cooling entirely. A failed compressor capacitor prevents the compressor from starting — you may hear a humming sound from the outdoor unit but no compressor operation. A dirty outdoor coil cannot reject heat effectively, causing the system to run continuously without satisfying the thermostat. The electronic expansion valve (EEV) may be stuck or failing, preventing proper refrigerant flow. Most of these issues require professional diagnosis with specialized tools.
Heat Pump Cooling vs Air Conditioner Cooling
A heat pump in cooling mode operates identically to a dedicated air conditioner. The refrigerant cycle reverses from heating mode using the reversing valve. In cooling mode, the indoor coil becomes the evaporator (absorbing heat from inside air) and the outdoor coil becomes the condenser (rejecting heat to outside air). The same refrigerant charge, compressor, and coils serve both functions. This means a refrigerant leak affects both heating and cooling performance. If your heat pump heats well but does not cool, the problem is specifically in the reversing valve or thermostat signal, not the refrigerant circuit.
When to Call a Technician
Call for professional service if: the system runs but produces no cool air, the outdoor unit is silent when the thermostat calls for cooling, you hear grinding or loud buzzing from the outdoor unit, you see ice on the indoor coil or refrigerant lines, the system short cycles on and off repeatedly, or you have noticed a gradual decline in cooling performance over several weeks. Refrigerant handling requires EPA certification and specialized equipment. Attempting to add refrigerant or open the sealed system without proper training is dangerous and illegal under Canadian regulations.