A heat pump is the same box doing two jobs, which is why heating problems and cooling problems often share a cause. If yours is blowing cold air when it should be heating, the symptom usually narrows the diagnosis quickly.
Blowing cold air in heat mode
The most common causes are a stuck reversing valve, a failed defrost control leaving the unit in the wrong cycle, low refrigerant charge, or a thermostat wired or configured for the wrong equipment type. A heat pump also runs cooler supply air than a furnace by design — around body temperature rather than hot — so check the temperature at a vent before assuming failure.
Ice on the outdoor unit
A light frost that clears during a defrost cycle is normal in a Sacramento winter. A thick jacket of ice that never clears is not. It points to a defrost board or sensor failure, a stuck outdoor fan, restricted airflow, or low charge. Do not chip the ice off — you will puncture the coil.
Running constantly or short cycling
Constant running means the system cannot reach the setpoint: low charge, a dirty coil, a duct leak, or equipment undersized for the load. Short cycling — on and off every few minutes — usually points to an electrical control, a failing capacitor, a restricted filter, or a thermostat placed where it reads the wrong air.
What a heat pump service call includes
- Mode and thermostat configuration verified first
- Refrigerant charge checked by superheat and subcooling in the operating mode
- Reversing valve and solenoid tested
- Defrost board and sensors put through a cycle
- Capacitor, contactor and amp draws measured
- Auxiliary and emergency heat operation confirmed
- Coils and airflow inspected, filter and static pressure checked
- Written estimate before any repair work begins
Repair or replace
Age, the cost of the specific repair relative to the equipment's remaining life, and whether the system uses a phased-out refrigerant are the honest inputs. A capacitor on a mid-life unit is an easy call. A compressor or a major refrigerant leak on an old system is where replacement deserves a real look — and we will say so plainly rather than push it. See our heat pump repair page for how we handle that conversation.
Frequently asked questions
Why does my heat pump blow cool air in heating mode?+
Supply air from a heat pump is naturally cooler than a furnace. If it is genuinely cold, look at the reversing valve, defrost control, refrigerant charge or thermostat setup.
Is ice on the outdoor unit normal?+
Light frost that clears during defrost is normal. Ice that stays put is a defrost, airflow or charge problem.
Should I run emergency heat?+
Use it to stay warm until a technician arrives, but it is electric resistance heat and costs more to run, so it is a stopgap, not a fix.
Do heat pumps work in Sacramento winters?+
Yes. Our winters stay well within the range modern heat pumps handle, and the same equipment cools the house in summer.
How often should a heat pump be serviced?+
Twice a year, because it runs in both seasons.
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