Heat Pump Not Heating in Hillsborough, CA

Heat Pump Not Heating in Hillsborough

Hillsborough sits in the Peninsula hills, and the higher, tree-shaded lots run cooler and damper than the open ones. That matters for heat pumps, because a coil tucked on a shaded, wooded side of a lot frosts over more readily on a cool, humid morning. A heat pump is built to handle that with a defrost cycle, but when the defrost control fails the coil ices, the outdoor unit loses its heat source, and the house stops warming up.

These are large estate homes, and many of them run more than one independent system across floors and wings. So a no-heat call here is usually one of two things: a single system or zone failing somewhere in a larger setup, or an iced coil on a unit placed in a cold, shaded pocket of the lot. The mild climate means the equipment is never working beyond its range, which is why these calls almost always come back to a specific component, not a system that cannot keep up.

The sloped, wooded lots also shape where the equipment sits and how the condensate drains, and that placement is part of the diagnosis. We trace the actual fault before quoting, and the diagnostic fee credits toward the repair on most jobs.

Common causes

Failed defrost control on a shaded coil. On a cool, damp Hillsborough morning the outdoor coil can frost, and the defrost board is supposed to reverse the cycle briefly to melt it. When that board or its coil sensor fails, the ice builds, the coil can no longer pull heat from outside air, and heating collapses. We confirm the defrost cycle initiates and the sensor reads correctly, then replace the board if it is not commanding defrost.

Outdoor coil iced over. If we arrive to a coil packed in ice, the defrost fault is usually the root cause, but a low refrigerant charge or a stuck fan can ice a coil too. We clear the ice, then determine why it formed instead of just thawing it and leaving. Treating the symptom without the cause means the homeowner calls back in a week.

Stuck reversing valve. The reversing valve flips the system into heating. A failed solenoid or a valve stuck mid-stroke leaves the unit running in cooling or stalled, so it blows unheated air on one system while others in the house are fine. We meter the solenoid and read line temperatures to confirm the valve shifted before replacing it.

Low refrigerant charge. A heat pump short on refrigerant loses heating capacity first and can also frost the outdoor coil. We find the leak with electronic detection rather than topping off, repair it, and weigh in the correct charge. On these estates only the affected system is usually low, so we isolate it.

Control board or zone fault on one system. With several systems and zoning across a large floor plan, a drifting control board or a damper stuck closed can drop heat to one wing while the rest of the house stays warm. We read the board status and test damper actuators to find the system that lost the call instead of guessing at the equipment.

How we diagnose it

The outdoor unit gets looked at first for ice on the coil, which immediately points at defrost or charge.
We confirm the defrost board initiates a cycle and the coil sensor is reading correctly.
Line temperatures verify whether the reversing valve actually shifted into heating.
Refrigerant pressures get checked against outdoor temperature to catch a low charge that frosts the coil.
On homes with more than one system, we map which system or zone is affected before touching the equipment.

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

Heat Pump Not Heating in Hillsborough: common questions

Do you service Hillsborough from your San Ramon base, and how quickly?

We do, and we run the Peninsula estates regularly. A no-heat call gets priority and we do our best to arrive same day, but we book an honest window rather than promise one we cannot hold, especially on the larger multi-system homes. Call (925) 999-4095.

My unit sits on the shaded, wooded side of the lot. Is that why it ices up?

It can contribute. A coil in a cool, damp, tree-shaded spot frosts more readily than one in the open, but the heat pump is designed to clear that with its defrost cycle. If it is icing and staying iced, the defrost control or the refrigerant charge is the real issue, and that is fixable. Placement and drainage are part of what we evaluate.

The outdoor unit is covered in ice. Do I need a new heat pump?

Almost never. A frosted coil on a winter morning is normal for a few minutes during a defrost cycle. A coil that stays packed in ice points to a failed defrost board, a low charge, or a stuck fan, all repairs, not a replacement. We clear it and find out why it iced rather than just thawing it.

Nearby and related

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

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