Heat pump not defrosting
Answer: call a hvac-technician.
Heat pumps naturally build frost on the outdoor coil in cold weather, and they run automatic defrost cycles every 30–90 minutes to melt it off. When defrost fails, ice encases the entire outdoor unit, blocking airflow and destroying efficiency — you'll notice lukewarm air from the vents and the compressor running constantly. Common causes are a faulty defrost control board or timer, a stuck reversing valve (which flips the system to cooling mode temporarily to defrost), a bad defrost thermostat or sensor, or a refrigerant leak that alters coil temperature. An HVAC technician can diagnose the failed component, replace the board, sensor, or valve, and verify proper defrost cycling before ice damages the compressor.
Who to call
For this problem, call a: hvac-technician
Symptoms to look for
- Thick layer of ice on the entire outdoor heat pump unit
- Lukewarm or cool air blowing from vents when set to heat
- Outdoor unit fan runs constantly but never switches to defrost mode
- Higher than usual electricity bills during heating season
- Compressor makes laboring or unusual sounds under heavy ice load