Heat Pump Not Cooling in Los Altos, CA

Heat Pump Not Cooling in Los Altos

Los Altos sits in California climate zone 4, with enough marine influence to keep most days moderate but warm afternoons that put real load on the AC side of a heat pump, especially across the big single-story ranch footprints common here. When a heat pump runs but won't cool, the cooling cycle has a fault. A heat pump cools by reversing its refrigerant flow, so we diagnose a no-cool heat pump the same way we'd diagnose any AC.

Many of these large ranches run two smaller systems split by wing rather than one big unit, so a no-cool problem often shows up in half the house, one zone going warm while the other holds. When that's the layout, it narrows the fault to one condenser and air handler instead of the whole home. We confirm the zoning setup before assuming it.

It's rarely a dead system. The unit that heated your home all winter still has a working compressor. Something cooling-specific has changed, a stuck reversing valve, a bad capacitor, a dirty coil, or low refrigerant from a leak, and each of those is a single-part fix with a number on a written estimate before we start. The one Los Altos wrinkle: many of these homes have additions and pop-ups that outgrew the original system, so we also check whether a room that never cools well is a fault or simply undersized airflow to an added space.

Common causes

Reversing valve stuck in heat mode. The reversing valve flips the heat pump between heating and cooling. When it sticks, the unit runs but blows warm air on a cooling call. We test the solenoid and read line temperatures to confirm, then replace the solenoid or valve. On a dual-zone ranch we check the valve on the specific system serving the warm wing.

Failed capacitor or contactor. The capacitor starts the compressor and fan; the contactor switches power to them. When one fails you'll often get the indoor fan running with no cold air. We meter both and carry common sizes on the truck, so this is usually a same-visit repair on the affected zone.

Low refrigerant from a leak. A system low on charge runs but can't pull enough heat out of the house, so the air comes out lukewarm. We find the leak first with electronic detection or a nitrogen pressure test, repair it, then evacuate and recharge to spec instead of just topping off and leaving you to call again in a month.

Dirty outdoor coil. A condenser coil packed with dust and yard debris can't reject heat, so head pressure climbs and cooling capacity falls. We clean the coil and clear its clearance, then recheck pressures. With two condensers on a dual-zone home, we confirm we're servicing the one tied to the warm zone.

Frozen indoor coil from low airflow. A clogged filter or weak blower starves the indoor coil and it ices over, killing cooling output. We thaw the coil, find why airflow dropped, and fix that. On Los Altos homes with additions, an undersized return to an added room can be the airflow problem, which we measure rather than assume.

Undersized system on an enlarged footprint. Not every won't-cool room is a broken part. Los Altos has a high rate of pop-ups and additions, and a system never resized for the bigger footprint simply can't keep one area cool on a warm day. We re-run the load on the current floor plan and tell you honestly whether it's a repair or a capacity problem.

How we diagnose it

Confirm which zone is affected and that its thermostat is actually calling for cooling, not stuck in heat.
On the affected system, verify the reversing valve shifts on a cooling call and test the capacitor and contactor.
Read suction and head pressures against outdoor temperature to judge charge and check for a leak.
Clean and inspect the outdoor coil serving the warm zone, and check the indoor coil and filter for ice.
If a specific room won't cool, measure airflow and check whether an addition outgrew the original system.

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

Heat Pump Not Cooling in Los Altos: common questions

Do you cover Los Altos from San Ramon, and how fast?

Yes, we run the South Bay regularly, including the 94022 and 94024 area. Call (925) 999-4095 for an honest arrival window. No-cool calls get priority routing on warm days, though same-day is best-effort rather than a guarantee.

One room has always been warm in summer. Is the heat pump broken, or is it something else?

Often it's neither broken nor a refrigerant problem. Los Altos has a lot of additions and pop-ups, and the original system frequently never got resized for the bigger footprint. We re-run the load on your current floor plan and tell you whether it's a repairable fault or an airflow and capacity shortfall, sometimes solved with a dedicated ductless head for that room.

It heated fine all winter but won't cool now. What's the likely cause?

If it heated fine, the compressor's healthy and the issue is cooling-specific. On these dual-zone ranches the usual suspects are a stuck reversing valve on one system or low refrigerant from a leak. Both are one-visit diagnostics. Our diagnostic is $75, credited toward the repair when it runs over $200.

Nearby and related

Heat Pump Not Cooling near Los Altos: Palo Alto · Mountain View · Cupertino .

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