Heat Pump Not Heating in Berkeley, CA

Heat Pump Not Heating in Berkeley

Berkeley leans on its heat pumps for heat more than for cooling, since the marine climate keeps summers cool. A good share of what we service here is ductless mini-splits, often retrofitted into older homes that never had ductwork. When one of those heads stops putting out heat, the house gets cold fast, because there is usually no backup gas furnace behind it.

A heat pump pulls heat out of the outside air and moves it indoors. On a damp Berkeley morning the outdoor coil collects frost, and the unit runs a defrost cycle to melt it. If the defrost sensor or board fails, ice builds on the coil until the unit can no longer extract heat. That is the most common reason a Berkeley mini-split stops heating: fog feeds frost, and a defrost fault stops the unit from clearing it.

It is almost always one part. A coil sensor that drifted. A defrost board that quit. A low charge from a small leak at a flare fitting. Berkeley winters rarely touch freezing, so the equipment is not being pushed past its limits. We find the failed component and write up the repair before doing the work.

Common causes

Defrost sensor or board fault. Berkeley's foggy mornings frost the outdoor coil regularly, so the defrost cycle gets a real workout. When the coil sensor drifts or the defrost board fails, ice builds and the unit can no longer pull heat from the air. We compare the sensor reading to actual coil temperature, watch a defrost cycle run, and replace the sensor or board.

Outdoor coil iced over. On a mini-split that has lost its defrost function, the outdoor coil can ice solid. The head blows cool air and the outdoor fan may labor. We thaw and inspect the coil, then trace why defrost stopped working rather than just clearing the ice and leaving.

Low refrigerant from a flare leak. Ductless systems join with flared fittings, and a slightly loose flare bleeds refrigerant slowly over a couple of seasons. Heating capacity drops before cooling does. We pressure-test, find the leak, reflare or replace the fitting, then weigh in the correct charge.

Reversing valve stuck in cooling. If the indoor head runs but blows air that never warms, the reversing valve may not be shifting into heat mode. We read line temperatures at the outdoor unit and confirm whether the valve is changing over, then replace the valve if it has failed.

Indoor unit communication or control fault. Mini-splits talk between the indoor head and outdoor unit over a control line. A fault code on the head, a corroded terminal, or a failed indoor board can leave the system idle or stuck. We read the unit's fault history, check the communication wiring, and isolate the failed board before quoting.

How we diagnose it

Confirm the head is calling for heat and the outdoor unit is responding, then read line temperatures to verify the reversing valve shifted into heat.
Inspect the outdoor coil for ice and watch a defrost cycle, checking the coil sensor against actual temperature.
Pressure-test for refrigerant loss, with attention to the flare connections common on ductless installs.
Read the unit's fault codes and check indoor-to-outdoor communication wiring for corrosion or loose terminals.

$75 diagnostic, credited toward any repair over $200. You get a written quote before any work begins.

Heat Pump Not Heating in Berkeley: common questions

Do you service Berkeley, or only the Tri-Valley?

We cover Berkeley and the inner East Bay along with our Tri-Valley core. Response on a no-heat call is best-effort same-day depending on the day's schedule, since Berkeley is a longer run from San Ramon than our home cities. Diagnostic is $75, credited toward a repair over $200.

Why does my mini-split lose heat on foggy mornings specifically?

Berkeley's fog frosts the outdoor coil, and the unit relies on its defrost cycle to clear it. When the defrost sensor or board has failed, those foggy mornings are exactly when ice builds faster than the unit can shed it, so heat output drops. Fixing the defrost fault fixes the morning problem.

My ductless head runs but only blows cool air. What is wrong?

Most often the reversing valve is not shifting into heat mode, the charge is low from a slow flare leak, or the outdoor coil is iced from a defrost fault. We read line temperatures and fault codes to tell which one it is before quoting anything.

Nearby and related

Heat Pump Not Heating near Berkeley: Oakland · Richmond .

This is usually a heat pump installation & service in Berkeley job. See our heat pump installation & service overview or the Berkeley service area.