Most heat pump repairs come down to a short list: a failed capacitor or contactor, an outdoor fan motor, a defrost control or sensor, a reversing valve that sticks, a refrigerant leak, or airflow choked by a dirty filter. In San Jose a heat pump heats through winter nights and cools through hot valley summers, so it runs in both seasons and its faults can appear in either. We find the failed part by testing, then give you the price before any work starts.
Normal, or a problem?
Several things look like faults and are not:
- Steam and a whoosh from the outdoor unit, with the fan stopped for a few minutes. That is defrost: the unit briefly reverses to melt frost off the outdoor coil.
- Air that feels warm rather than hot. Heat pump air is cooler than furnace air even when everything works. Judge it by whether the house holds the setting.
- Light frost on a cold, damp morning that clears within a cycle.
- “Aux heat” on the thermostat for short stretches, during defrost or after a big jump in the setting.
- Long, quiet run times on variable-speed models, which are built to run low and steady.
What is not normal: ice that covers the coil and stays, aux heat that never switches off, cool air in heat mode, or a breaker that trips again after a reset. If the coil is a block of ice, switch the system off (or to emergency heat if you have backup heat) and call. Do not chip at the ice; the fins bend easily. More in heat pump freezing.
Common faults and what they usually take
| What you notice | Likely cause | What it usually takes |
|---|---|---|
| Cool air in heat mode, or warm air in cool mode | Reversing valve or its solenoid; wrong thermostat setting | Thermostat check, solenoid coil or valve repair |
| Outdoor unit hums, fan does not spin | Capacitor or fan motor | Capacitor or motor replacement |
| Ice that does not clear | Defrost board or sensor, low refrigerant, fan fault | Defrost test, sensor or board, leak search |
| Turns on and off every few minutes | Thermostat placement, low charge, electrical fault | Testing before any part is changed |
| Runs constantly, bills climbing | Dirty coils, refrigerant leak, aux heat stuck on | Coil cleaning, leak repair, control check |
| Rattling, buzzing or screeching | Loose panels, fan blade hitting ice, failing contactor or motor | Inspection and repair |
Heating mode, cooling mode and the reversing valve
A heat pump switches between heating and cooling with a reversing valve moved by a small solenoid. The thermostat drives it through a terminal marked O or B, depending on the brand. After a thermostat replacement, a wrong O/B setting is one of the most common reasons a heat pump cools when it should heat, and it needs no parts to fix. See thermostat installation and thermostat not working. A failed solenoid coil is an electrical part; a failed valve body is refrigerant work.
Refrigerant: find the leak, do not just top it off
A heat pump that is low on refrigerant has a leak, and adding refrigerant without finding it means paying again next season. Our EPA-certified technicians keep the system on the refrigerant it was built for. Older units use R-22, which is no longer produced, so recharging them is costly; most newer ones use R-410A, and equipment built since 2025 uses lower-impact refrigerants. On an older R-22 unit, a major leak or a failed compressor is usually the point to compare repair with a new heat pump.
What affects the price
Most heat pump repairs run $125–$700. Capacitors, contactors, thermostat settings and defrost sensors sit at the low end; fan motors, defrost boards and leak repairs cost more. A compressor, a reversing valve replacement or a large leak on an older system can go past that range, and that is when replacement belongs in the conversation. Our repair-or-replace guide helps with the numbers. The diagnostic fee is waived if you go ahead with the repair.
Ductless and dual-fuel systems
Mini-splits are heat pumps too, with inverter boards and indoor units that show error codes; see mini-split repair. In a dual-fuel system the gas furnace stays in the loop, and some “heat pump” complaints turn out to be furnace repairs. With any gas appliance in the house: if you smell gas, leave and call the gas utility or 911 from outside; if a CO alarm sounds, get everyone out.
San Jose notes
- Evergreen: foothill streets cool off faster after dark than the valley floor, so defrost runs more often on winter mornings and a weak defrost sensor shows up sooner.
- Blossom Valley: in warm South San Jose summers, a heat pump losing capacity often shows up first as a high cooling bill. A dirty outdoor coil is the usual first suspect.
- Cambrian and Willow Glen: in 1950s–60s homes with leaky attic ducts, a heat pump’s milder supply air makes duct losses easier to feel, so a cold room may need duct work rather than a part.
- Attic air handlers: in summer a clogged condensate drain trips the float switch and shuts the system off, sometimes after a stain appears on the ceiling below.
Before you call
Check the thermostat mode and setting, replace a dirty filter, and make sure both breakers are on: one for the outdoor unit, one for the indoor unit. Keep a couple of feet clear around the outdoor unit. Same-day service is available for most calls received before noon, and urgent calls are taken 24/7 through emergency HVAC.