Furnace Not Heating in Hillsborough, CA

Furnace Not Heating in Hillsborough

A furnace that won't produce heat is, in the great majority of cases, one fixable part: a cracked hot surface igniter, a flame sensor glazed with carbon, a high-limit switch tripped by a choked filter, or a control board that dropped a relay. None of that means a dead system. In Hillsborough the diagnosis is usually shaped by the size of the house, because many of these properties carry more than one heating system covering different floors or wings.

The town sits up in the Peninsula hills, and the higher, tree-shaded lots stay cooler than the bayside flats, so the heat earns its keep here through the winter. When a homeowner says the furnace isn't heating, it often turns out one of several systems is down, frequently the one serving an upper or shaded section of the house. A single dead zone narrows the search fast: the fault sits in that one system or its controls, not the gas service or the thermostat platform for the whole estate.

Where the systems are different ages, the failure could be an igniter on the older unit, a drifting board on a newer zone, or a stuck zone damper masquerading as no heat. The lots matter too. On sloped, wooded ground, equipment and condensate routing end up in awkward spots, and that's where we start when one system quits.

Common causes

One system down on a larger multi-system home. When an upper floor or one wing goes cold, the fault is usually contained to that system. We identify the air handler serving the cold area and diagnose it directly, leaving the working systems untouched.

Cracked hot surface igniter. The most common no-light failure on forced-air furnaces. Years of heat cycling crack the igniter and it stops glowing. We test resistance and continuity and replace it, $200 to $350. The older unit in the house is usually first to go.

Dirty flame sensor. If a system lights then drops out after a few seconds, the flame sensor is carboned and the board can't prove flame, so it shuts the gas off. Cleaning usually fixes it; a worn sensor is $150 to $200 to replace.

Stuck zone damper. On a zoned estate system, a damper that won't open leaves a floor feeling unheated even though the furnace is firing. We test the damper motors and zone panel to separate a distribution problem from a heat-production problem.

Limit switch tripped by a dirty filter. A neglected filter on one of several systems starves airflow, overheats the heat exchanger, and trips the high-limit. We confirm filter condition and airflow and check whether the limit reset or failed closed.

Control or zone board fault. Where systems age at different rates, a heat relay or zone board can fail and leave one system unable to deliver heat. We meter the board's outputs before condemning it, since boards are among the costlier furnace parts.

How we diagnose it

Identify which of the home's systems serves the cold area and isolate the diagnosis to that unit.
Separate a heat-production fault from a distribution fault by testing zone dampers and the zone panel.
Run the full ignition sequence and meter igniter, flame sensor, and limit switch on the affected furnace.
Test control and zone board outputs before condemning expensive boards.
Meter carbon monoxide and inspect the heat exchanger on the affected gas system before leaving.

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

Furnace Not Heating in Hillsborough: common questions

Do you come out to Hillsborough, and how quickly?

Yes. We service Hillsborough and the Peninsula regularly. We're San Ramon based and run the full Bay Area, with no-heat calls routed ahead of routine work. Call (925) 999-4095 for an honest arrival window.

The cooler, shaded part of our house lost heat. Is that the climate or the equipment?

The shaded upper and hillside sections of Hillsborough homes do run cooler and lean on heat more, which can make a marginal furnace fail there first. But a zone that's gone fully cold is an equipment fault, usually an igniter, flame sensor, or zone damper on that system, not the weather. The $75 diagnostic is credited toward any repair over $200.

Could the whole estate's heat be out from one bad part?

Rarely, and only if it's a shared point like the thermostat platform or the gas service. When a home runs more than one system, a single failure usually takes down just one zone. That keeps the repair smaller and cheaper, and we confirm which system is at fault before quoting anything.

Nearby and related

Furnace Not Heating near Hillsborough: Menlo Park · Palo Alto .

This is usually a furnace repair in Hillsborough job. See our furnace repair overview or the Hillsborough service area.