Furnace Not Heating in Portola Valley

Furnace Not Heating in Portola Valley

A furnace that won't produce heat is, in the large majority of cases, one fixable part: a cracked igniter, a flame sensor coated in carbon, a high-limit switch tripped by a dirty filter, or a control board that dropped a relay. None of it means the system is finished. In Portola Valley, the diagnosis often depends on the property's layout, since the larger custom homes on wooded acreage and some ranch properties toward Skyline run more than one system covering different additions or wings.

The oak-and-redwood hill lots off Alpine Road and Portola Road hold cooler, damper air than the open valley, so the shaded and wooded sections of a property lean harder on the furnace through winter. When someone tells us their furnace isn't heating, it's often one of several systems that failed, frequently the one covering a wing built later or set into a shadier part of the lot. A single dead system narrows things quickly: the fault sits in that unit or its controls, not the gas service or the thermostat for the whole house.

On properties with well and septic setups on the outer roads, equipment sometimes ended up in awkward spots to keep clear of those systems, and that placement is part of what we check when one furnace quits while the others keep running.

Common causes

One system down on a property with more than one furnace. When one wing or addition goes cold while the rest of the house stays warm, the fault is almost always contained to that system. We identify the unit serving the cold area and diagnose it directly without touching the systems that are working fine.

Cracked hot surface igniter. The most common no-light failure on a forced-air furnace. The ceramic element cracks after years of heat cycling and stops glowing. We provide a written repair estimate after the on-site diagnosis and before any work starts. On a property with an older original furnace and a newer one added later, the older unit usually goes first.

Dirty flame sensor. If a system lights and drops out within seconds, the flame sensor is carboned over and the board can't confirm flame, so it shuts the gas off. This turns up more on a furnace serving a wing that isn't used year-round. We provide a written repair estimate after the on-site diagnosis and before any work starts.

Stuck zone damper. On a zoned system covering a larger custom home, a damper that won't open leaves one section feeling unheated even while the furnace fires normally. We test the damper motors and zone panel to tell a distribution problem apart from an actual heat-production fault.

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

Control or zone board fault. Where the property's systems are different ages, a heat relay or zone board can fail and leave one unit unable to produce heat. We meter the board's outputs before condemning it, since boards run among the more expensive furnace parts.

How we diagnose it

• Identify which system on the property serves the cold wing or addition and isolate the diagnosis to that unit.
• Testing the zone dampers and zone panel tells us whether it's a heat-production fault or a distribution fault.
• We run the affected furnace through its full ignition sequence and meter the igniter, flame sensor, and limit switch.
• We test the control and zone board outputs first, before writing off an expensive board.
• Before leaving, we meter carbon monoxide and check the heat exchanger on the affected system.

$99 diagnostic, credited toward the repair. You get a written quote before any work begins.

Furnace Not Heating in Portola Valley: common questions

Nearby and related

Furnace Not Heating near Portola Valley: Woodside · Menlo Park · Los Altos Hills .

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