Heat Pump Not Heating in El Cerrito
El Cerrito leans on heat pumps for heat more than for cooling, since the marine layer keeps the flats cool and even the hillside above the fog line gets chilly mornings. A growing share of what we service here is ductless mini-splits, retrofitted into ranches and split-levels off Moeser Lane and Barrett Avenue that never had ductwork, alongside the original wall and floor furnaces still running in older homes. When a mini-split stops heating, the house cools fast, since there's often no backup furnace behind it.
A heat pump pulls heat from the outside air and moves it indoors. On a foggy El Cerrito morning the outdoor coil collects frost, and the unit runs a defrost cycle to clear it. When that defrost sensor drifts or the board quits, frost keeps piling onto the coil and the unit loses its ability to draw heat from the air. That's the most common reason a mini-split here stops heating: hillside fog feeds frost, and a defrost fault stops the unit from shedding it.
It's almost always one part. A coil sensor that drifted. A defrost board that quit. Refrigerant that's slowly leaked out through a loose flare joint. El Cerrito winters rarely touch freezing, so the equipment isn't being pushed past its design limits. We track down which part failed and put the fix in writing before any work starts.
Common causes
Defrost sensor or board fault. El Cerrito's foggy mornings, especially in the flats near San Pablo Avenue, frost the outdoor coil regularly, so the defrost cycle gets real use. When the coil sensor drifts or the defrost board fails, ice builds and the unit can't pull heat from the air. Our check: measure actual coil temperature against what the sensor reports, observe the unit through a full defrost cycle, and swap out whichever part, sensor or board, is off.
Outdoor coil iced over. On a mini-split that's lost its defrost function, the outdoor coil can ice solid. Indoors you get a stream of cool air off the head, and the outdoor fan can start struggling against the buildup. We thaw and inspect the coil, then trace why defrost stopped working rather than just clearing the ice.
Low refrigerant from a flare leak. Ductless line sets running through hillside walls join with flared fittings, and a slightly loose flare bleeds refrigerant slowly over a couple of seasons. Heating capacity drops before cooling does. Our fix: pressure-test the line set to locate the leak, redo or swap the flare fitting, then charge the system back to spec by weight.
Stuck reversing valve. When the indoor head is running yet the air coming out never gets warm, the culprit is often a reversing valve that isn't switching over into heat mode. We read line temperatures at the outdoor unit and confirm whether the valve is changing over, then replace it if it's failed.
Control signal fault between head and outdoor unit. The indoor head and outdoor unit stay in sync over a low-voltage control line. A fault code on the head, a corroded terminal, or a failed indoor board can leave a hillside retrofit idle or stuck. We read the unit's fault history, check the wiring, and isolate the failed board before quoting.
How we diagnose it
- Verify the head is sending a heat call and the outdoor unit answers it, then check line temperatures to confirm the reversing valve actually shifted over.
- Look over the outdoor coil for frost buildup and run through a defrost cycle, comparing what the sensor reads to the coil's real temperature.
- Pressure-test for refrigerant loss, with attention to the flare connections common on El Cerrito's retrofit installs.
- Pull the stored fault codes and check the wiring between indoor and outdoor units for corrosion or a loose terminal.
$99 diagnostic, credited toward the repair. You get a written quote before any work begins.
Heat Pump Not Heating in El Cerrito: common questions
Why does my mini-split lose heat specifically on foggy hillside mornings?
My mini-split runs but only blows cool air. What's wrong?
Do you cover El Cerrito, or just Berkeley and Richmond?
Nearby and related
Heat Pump Not Heating near El Cerrito: Richmond · Albany · Berkeley .
This is usually a heat pump installation & service in El Cerrito job. See our heat pump installation & service overview or the El Cerrito service area.
Heat Pump Not Heating in El Cerrito
Repairs start with a $99 diagnostic, credited toward the fix. Replacing a system? The on-site assessment visit is free. Same-day written findings either way.
Bay Area · 7am–7pm · 7 days · no overtime charges