Heat Pump Not Cooling in Atherton, CA

Heat Pump Not Cooling in Atherton

Atherton sits on the Peninsula, mild and a touch warmer than the coast, with the hottest afternoons climbing into the 80s and occasionally higher. Cooling load is moderate, which makes heat pumps an efficient year-round fit for the large floor plans here. The homes are big, and many run more than one system so different parts of the house can be conditioned on their own. So when cooling fails, the first job is figuring out which system is down, and whether it's the refrigerant side or the zoning.

A heat pump cools on the same cycle as an air conditioner, with a reversing valve added to flip between heating and cooling. When it won't cool, we work the same diagnostic an AC gets and add the valve to the suspect list. A whole system blowing warm points to the refrigerant circuit: a stuck reversing valve, a low charge from a leak, a dead capacitor or burned contactor. One warm zone in an otherwise cold house points to a zone damper or a control board instead.

On a house running several air handlers with zoning dampers, the failure points multiply, and a single drifted board or stuck damper can leave one part of the home uncomfortable while everything else holds temperature. That's not a dead system. It's one fault we trace, rather than swapping the easy part and hoping it sticks.

Common causes

Reversing valve stuck in heat mode. The reversing valve flips a heat pump between heating and cooling, and it can stick on the heat side. The system runs but moves heat into the house. We energize the solenoid, confirm the valve shifts, and read line temperatures to verify flow direction before condemning an expensive part on premium ducted equipment.

Control board or zoning damper fault. On a zoned system, one part of the house running warm while another stays cold usually means a zone board that drifted or a damper actuator that won't open. We trace the actual fault through the controls in order instead of replacing a board blind, because most of these calls come down to a sensor or a wiring issue.

Low refrigerant from a leak. A slow leak drops the charge until a system runs but won't pull heat out of the house. We pressure-test the affected circuit, find the leak, repair it, and weigh in the correct charge rather than topping off a system that will lose it again.

Failed capacitor or contactor. A dead run capacitor or pitted contactor stops the compressor or condenser fan from starting, so one outdoor unit sits quiet while its air handler blows warm. We test capacitance against the rated value and inspect the contactor. It's the quickest fix on a no-cool call.

Dirty outdoor coil. An outdoor coil fouled with dust and landscaping debris can't reject heat, so head pressure rises and cooling falls off. We inspect and clean the coil and confirm the condenser fan is moving full air across it.

Frozen indoor coil from low airflow. A clogged filter or weak blower on a large air handler drops airflow until the coil freezes and stops cooling. We thaw it, fix the airflow restriction, and verify static pressure so it holds.

How we diagnose it

Pin down which of the home's systems is down and whether the whole system or one zone is warm
On a zoned system, step through the zone board and damper actuators before replacing any controls
Read pressures and line temperatures to confirm the reversing valve switched and the charge is right
Bench-test the run capacitor and inspect the contactor on the condenser that's affected
Inspect and clean the outdoor coil, then check the indoor coil and filter for ice or restricted airflow

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

Heat Pump Not Cooling in Atherton: common questions

Do you cover Atherton from your East Bay base?

Yes. We're based in San Ramon and service the Peninsula including Atherton and the 94027 area. Drive time is longer than our East Bay core, so we'll give you an honest window when you call rather than promising same-day across the board. Call (925) 999-4095.

With a mild Peninsula climate, is one system out of several urgent?

It depends which part of the house it serves. Atherton summers only push hard on the hottest afternoons, so a system serving rooms you're not using can often wait for a scheduled repair. If it's the system over occupied bedrooms during a warm stretch, we prioritize it. And because the same heat pump heats in winter, a cooling fault now can mean a heating fault later, so it's worth fixing the root cause once.

One part of the house won't cool but the rest is fine. What's wrong?

A single warm zone in an otherwise cold house almost always means a zoning fault: a stuck damper, a drifted zone board, or a thermostat in the wrong mode, not the refrigerant circuit. If a whole system blows warm, then we look at the reversing valve, charge, and capacitor. We confirm which before writing the estimate.

Nearby and related

Heat Pump Not Cooling 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.