Heat pump repair in Menlo Park, Atherton and Portola Valley starts with a question a furnace never raises: does the problem show up in heating, in cooling, or both? A heat pump uses one refrigerant circuit, one compressor and a reversing valve to do two jobs, so a fault can hide in one mode and look fine in the other. We test both modes, the controls, airflow, defrost, the electrical parts and the refrigerant readings before anyone talks about a new system. Many heat pumps here are recent retrofits into older ranch homes, which brings its own set of faults.
Normal behaviour that looks like a fault
- Warm, not hot, air. A heat pump delivers gentler heat than a gas furnace and runs longer cycles. That is how it is meant to work.
- Defrost. On cool, damp mornings frost builds on the outdoor coil. The unit reverses for a few minutes to melt it: the outdoor fan stops, you may hear a whoosh as the valve shifts, and steam rises.
- A brief cool spell indoors during defrost, unless backup heat covers it.
- The outdoor unit humming along on a mild night. Variable-speed units often run slowly for hours instead of switching on and off.
Symptoms and likely causes
| What you notice | Likely cause | What it usually takes |
|---|---|---|
| Cool air in heat mode, cools fine in summer | Reversing valve or its solenoid, thermostat set for the wrong valve type | Control test, then solenoid, valve or setup |
| Heats but will not cool | Valve stuck in one position, same thermostat setting | Valve or solenoid repair, setup fix |
| Outdoor unit iced over for hours | Defrost control or sensor, outdoor fan, low charge | Defrost repair, fan motor or leak search |
| Outdoor unit hums, fan still | Failed capacitor or fan motor | Capacitor or motor |
| Runs constantly, house barely warm | Low charge, dirty coil, restricted airflow | Leak repair, cleaning or airflow work |
| High bill, outdoor unit seldom runs | Stuck on emergency or backup heat | Thermostat and control setup |
| Error code on a head or thermostat | Sensor or communication fault | Testing that code’s circuit |
Roof runoff dripping onto the outdoor unit can also freeze it in a block on a cold morning, so the gutter above it is worth a look.
Faults that show up after a retrofit
When a heat pump replaces a gas furnace in an older house, the equipment is new but the house is not. The faults traced most often:
- Thermostat settings carried over from the furnace. A wrong valve setting, backup heat allowed to start too early, or a deep overnight setback that forces backup heat every morning.
- Ducts that were fine for a furnace. A heat pump moves more air for the same heat. Undersized returns and crushed attic runs raise static pressure, and the system never delivers its capacity.
- Charge not adjusted for a long line set, common where the outdoor unit sits far from the indoor unit, as on hillside Portola Valley lots and large Atherton properties.
- Condensate drains from attic air handlers that clog in the first cooling season.
- Dual-fuel changeover set so the furnace runs on days the heat pump could carry the load.
Refrigerant: a recharge is not a repair
A heat pump does not use up refrigerant. A low charge means a leak: at a flare fitting on a ductless line set, the outdoor coil, a service valve or the indoor coil. Recharging without a leak search books the next visit. The repair is to find and fix the leak, pull a vacuum where the circuit was opened, and weigh in the correct charge. Older heat pumps on R-22 are costly to recharge because that refrigerant is no longer made or imported in the US, so a major leak on one usually starts a replacement conversation.
Compressor and outdoor unit checks
Before a compressor is condemned, its electrical side gets tested: the capacitor, the contactor, winding resistance and amp draw under load. A compressor that will not start often has a failed capacitor or contactor, which is a far smaller repair. The outdoor coil is cleaned and inspected; dust, pollen and leaves packed into the fins cut both heating and cooling.
Ductless heat pumps
Mini-split heads have their own faults: clogged head filters and coils, drain lines that drip down the wall, stuck louvers, condensate pumps, and communication errors between the head and the outdoor unit. Before calling, clean the head filters, check the remote’s batteries and mode, and note any blinking pattern on the head.
What moves the price
Most heat pump repairs fall between $89 and $700. Capacitors, contactors, defrost sensors and thermostat setup sit at the low end. Fan motors, reversing valve solenoids and leak repairs cost more. Replacing the valve itself takes more labor because the refrigerant circuit has to be opened and brazed. Inverter control boards and compressors can go above the range.
Repair or replace
Repair one failed part on a heat pump that otherwise runs well. When an older unit needs a compressor, a reversing valve or a large leak repair, or still runs on R-22, compare the cost with a new heat pump installation. With a dual-fuel system, a heating failure may be on the furnace side; see furnace repair.
Before you call
- The thermostat is on Heat or Cool, not left on emergency heat.
- Filters are clean, indoors and on any ductless heads.
- The outdoor unit is clear of leaves and plants.
- Do not chip ice off the coil; the fins bend easily. If it is iced solid, switch to emergency heat if you have it, and call.
- Breakers are on. If one trips again, leave it off.