Heat Pump Not Heating in Los Altos, CA

Heat Pump Not Heating in Los Altos

When a heat pump stops heating, the panic reaction is to assume the whole unit is shot. In nine cases out of ten it is not. A heat pump is a refrigeration circuit running in reverse, and when it stops making heat the failure usually traces to one component. Often it is a reversing valve stuck in cooling mode. Sometimes a fouled defrost control, a contactor that won't pull in, or a refrigerant charge that has slowly bled down over a few seasons. The compressor and the coils are usually fine.

Los Altos winters are mild, with marine influence keeping mornings cool but rarely cold enough to push a standard heat pump out of its operating range. So an outdoor unit struggling to make heat here is reporting a fault, not hitting a climate wall. The bigger Los Altos wrinkle is the housing. A lot of these are larger single-story homes running dual-zone equipment. When one zone goes lukewarm and the other is fine, the problem is frequently a zone damper or a single zone's air handler, not the outdoor condenser at all.

We diagnose to the part. The point of the visit is to tell you which component failed, what it costs, and whether the rest of the system has the life left to justify the repair. All of it goes on a written estimate before we touch anything.

Common causes

Reversing valve stuck in cooling. The reversing valve is what lets a heat pump run backward to make heat. When its solenoid sticks or the valve body hangs mid-stroke, the unit keeps pumping cold air in winter. We confirm it by reading line temperatures across the valve and checking solenoid coil voltage. Sometimes it is a failed solenoid coil, a cheap fix; sometimes the valve body itself is stuck, which is a brazed-in repair.

Low refrigerant charge. A slow leak drops capacity until the system can no longer pull enough heat from outside air. The tell is long run times with weak warm air and sometimes ice on the outdoor coil. We hook up gauges, check superheat and subcool against the unit's spec, and find the leak with electronic detection or dye. We fix the leak first, then recharge. Recharging without finding the leak just buys a few months.

Defrost control fault. Heat pumps frost up in cold, damp mornings and run a defrost cycle to clear the outdoor coil. A bad defrost board or sensor leaves the coil iced over, and an iced coil cannot absorb heat. We watch a defrost cycle, check the sensor resistance, and confirm the board is timing and terminating correctly.

Failed contactor or capacitor. The contactor is the relay that powers the outdoor unit; the capacitor gives the compressor and fan motor their starting kick. A pitted contactor or a weak capacitor leaves the condenser silent or humming without starting. Both are common, both are fast to test with a meter, and both are stocked on our truck.

Aux heat strips not engaging. Most ducted heat pumps have electric backup heat for the coldest mornings or for when the heat pump is in defrost. If the strips or their sequencer fail, the system can fall behind on a cold start and feel like it is barely heating. We check strip continuity, the sequencer, and the control wiring that calls for backup heat.

Zone damper or single-zone air handler. On the dual-zone systems common in larger Los Altos homes, one zone going cold while the other stays warm points away from the outdoor unit. We check the zone control board, the damper motors, and the affected zone's air handler before assuming a compressor problem.

How we diagnose it

Confirm the thermostat is actually calling for heat and reading the right mode, then verify the outdoor unit responds to that call.
Read line temperatures across the reversing valve to confirm the system is in heating mode, not stuck in cooling.
Put gauges on the system and check superheat and subcool against the unit's spec to confirm the charge.
Inspect the outdoor coil for ice and watch a defrost cycle if conditions allow.
Meter the contactor, capacitor, and on dual-zone homes the zone board and damper motors before quoting any part.

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

Heat Pump Not Heating in Los Altos: common questions

Do you actually cover Los Altos, or are you based across the bay?

We are based in San Ramon and run the whole Bay Area, Los Altos included. South Bay calls get scheduled around traffic windows so we are not stuck on the 880 during your appointment. Call (925) 999-4095 and we will give you an honest arrival window, not a vague four-hour block.

Los Altos winters are mild, so should my heat pump ever struggle to keep up?

No. Winters here are not cold enough to push a working heat pump out of its range, so if yours is falling behind on a normal winter morning, that is a fault to diagnose, not the climate. A common culprit in larger Los Altos homes is a system that was never resized after an addition, so it is undersized for the current footprint.

My heat pump is blowing air but it feels cool. Is the whole thing dead?

Almost certainly not. Cool air from a unit that is still running usually means it is stuck in cooling mode (reversing valve), low on refrigerant, or iced over from a defrost fault. Those are component repairs. The $75 diagnostic tells you exactly which one, and it is credited toward any repair over $200.

Nearby and related

Heat Pump Not Heating 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.