Heat Pump Not Heating in Atherton, CA

Heat Pump Not Heating in Atherton

Larger Atherton homes often run more than one heat pump, with separate systems serving different wings and zoning dampers layered on top. So when an owner says the heat pump is not heating, the first job is figuring out whether the whole property lost heat or just one system or one zone. Those are very different problems, and which wing went cold tells us where to look.

Winters on the Peninsula are mild and rarely freeze, so a heat pump covers the heating and the moderate cooling these homes need without any cold-climate equipment. A no-heat call here is almost always a failed component or a control fault, not a system that is undersized for the weather. On some of the older estates we find equipment that was sized loosely rather than to a real load calculation, which short-cycles and leaves rooms uneven even when nothing is technically broken.

Houses with several systems give you more places for a fault to hide, not a bigger fault. We trace where it actually is across the controls, dampers, and equipment rather than swapping the easy part and hoping. The diagnostic fee credits toward the repair on most jobs.

Common causes

Reversing valve stuck on one system. When a house has more than one condenser and only one wing goes cold, the reversing valve on that system is a prime suspect. If its solenoid fails or the valve sticks, that system runs in cooling or stalls between modes while the others heat normally. We isolate the affected system, check the solenoid, and read line temperatures to confirm before replacing the valve.

Zone damper stuck closed. On a zoned estate, a damper that fails closed starves heat to that zone even though the heat pump is producing it fine. The room stays cold while the rest of the house is comfortable. We test each damper actuator and the zone board outputs to find the one that is not opening, then repair the actuator or board rather than the equipment.

Drifting or failed control board. Multi-zone control and communicating boards drift over time, and on these systems a board fault can drop one system out of heating entirely. We read the board status and fault codes, confirm it is commanding the reversing valve and stages correctly, and replace the board when it has lost the call rather than guessing at refrigerant.

Low refrigerant on one of the systems. With multiple independent systems, only one is usually low, and it is the one that quit heating. A heat pump short on charge loses heating capacity first. We locate the leak on that specific system, repair it, and weigh in the correct charge instead of topping off every unit on the property.

Contactor or capacitor failure. A failed contactor or weak start capacitor takes a whole condenser offline, so one system stops heating while its neighbors run. These are common, inexpensive failures. We meter the capacitor and inspect the contactor on the affected unit and carry both on the van.

How we diagnose it

We map which systems and which zones are affected so we know whether it is one unit, one zone, or the whole house.
Fault codes come off each system control board before we touch the equipment.
Zone damper actuators and outputs get tested to rule out a stuck-closed damper starving the room.
On the affected system, line temperatures tell us whether the reversing valve shifted into heating.
We check refrigerant charge on the specific system that quit, not on the units that are still working.

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

Heat Pump Not Heating in Atherton: common questions

You are based in San Ramon. Do you really cover Atherton on the Peninsula?

Yes. We work the Peninsula estates regularly and route Atherton calls out of our San Ramon base. For a no-heat call we prioritize and do our best to come same day, but on a multi-system estate we would rather book a real window than promise one we cannot keep. Call (925) 999-4095.

With more than one system on the property, do I have to replace all of them when one fails?

No. These are independent systems, and a failure in one has nothing to do with the others. We diagnose and repair the system that quit. If a unit is genuinely at end of life we will tell you on a written estimate, but one bad reversing valve or contactor does not condemn the whole property.

Half the house is warm and half is cold. What does that tell you?

It usually means the problem is in one system or one zone, not the heat pump as a whole. That points us at a stuck reversing valve, a zone damper that failed closed, or a control board that lost the heat call on that system. We start by mapping which zones are affected, which narrows it fast.

Nearby and related

Heat Pump Not Heating near Atherton: Menlo Park · Palo Alto .

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