Heat pump icing up in summer — San Jose, California
Ice forming on the outdoor heat pump unit or indoor evaporator coil during summer cooling is a clear sign something is wrong — the system is overcooling the refrigerant below the freezing point of condensation on the coils. The most common cause is restricted airflow: a dirty air filter, blocked return vents, or a failed blower motor. Low refrigerant charge (from a leak) is the second most common cause — less refrigerant means lower coil temperature and ice buildup. Other causes include a stuck or failed defrost board (on reversing models), a dirty evaporator coil, or a malfunctioning thermostatic expansion valve (TXV). An HVAC technician checks refrigerant charge, inspects the filter and coil, measures superheat and subcooling, and fixes the root cause. Running a frozen system damages the compressor — turn it off and let it thaw before a technician arrives.
Who to call
For this problem in San Jose, call a: Klimaattechnicus
Vind een Klimaattechnicus in San JoseSymptoms to look for
- Visible ice or frost coating on the outdoor unit's coil or refrigerant lines
- Indoor vents blowing warm air or barely any air at all
- Water dripping or pooling around the indoor air handler as ice melts
- System short-cycling — turning on and off every few minutes
- Unusual hissing or bubbling sound near the indoor coil (possible refrigerant leak)