Heat Pump Making Unusual Noises — What Each Sound Means
Published: July 15, 2026 — BC Wide Home Services Ltd, doing business as BC Wide Heating & Air Conditioning — Greater Vancouver, BC
Clicking Sound When Starting or Stopping
A single click when the heat pump starts or stops is normal — this is the contactor engaging or disengaging to supply power to the compressor and fan. Rapid clicking that repeats without the unit starting indicates a failing contactor, a failed capacitor, or a control board problem. If the outdoor unit clicks but does not start, turn it off at the thermostat and breaker to prevent damage to the compressor, and call for professional service. Repeated clicking that eventually leads to startup usually indicates a weakening capacitor that should be replaced proactively before complete failure.
Grinding or Metal-on-Metal Noise
Grinding sounds from the outdoor unit indicate a serious problem — typically a failing compressor bearing or a failing outdoor fan motor bearing. These components are sealed and cannot be lubricated. A grinding compressor will eventually seize, potentially releasing metal debris into the refrigerant system that contaminates the entire circuit. Turn off the system immediately at both the thermostat and circuit breaker. Continuing to operate a grinding compressor dramatically increases the repair cost. In some cases, only the compressor needs replacement. In severe cases where debris has circulated, the entire system may need replacement.
Buzzing or Humming from Outdoor Unit
A loud buzzing or humming from the outdoor unit that is louder than normal operation usually indicates a failing compressor capacitor or a failing contactor. The capacitor provides the electrical boost to start the compressor motor. When it fails, the compressor may hum but not start, drawing high current that can trip the breaker or overheat the compressor windings. A buzzing contactor has burned or pitted contacts that create electrical resistance and vibration. Both issues are repairable — a capacitor replacement costs approximately 150-300 dollars, and a contactor replacement costs approximately 200-350 dollars.
Whooshing or Gurgling Sounds Inside
Whooshing or gurgling sounds from the indoor unit during operation are typically normal — this is the sound of refrigerant flowing through the expansion valve and evaporator coil. However, if the sound becomes loud or includes bubbling, it may indicate air in the refrigerant lines or a refrigerant leak that has allowed non-condensable gases into the system. Gurgling sounds from a wall-mounted indoor unit can also indicate a partially blocked condensate drain — water is backing up inside the drain pan and air is being pulled through standing water in the drain line. This should be addressed before water overflows from the unit.