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Serving San Jose and nearby cities Mon–Fri: 8 AM–8 PM · Requests accepted 24/7 · (669) 201-9530

Sunnyvale Furnace Repair

The short answer

Sunnyvale furnace failures usually involve the igniter, flame sensor, inducer, pressure switch, limit switch or blower. EliteAir watches the startup sequence to pinpoint the fault, makes the repair, and checks venting and combustion before leaving.

In Sunnyvale, a furnace may sit unused for six or seven months a year, then get called on hard during a run of cold, wet nights in December and January. That pattern is tough on certain parts. Igniters that were fine last spring crack on the first start, flame sensors gather residue, and blower motors that sat still all summer struggle to get moving. Many furnaces here are tucked into garages, hall closets or attics of mid-century homes, often sharing space with a water heater and boxes of stored belongings. EliteAir Heating & Cooling repairs gas furnaces throughout Sunnyvale, ZIP codes 94085, 94086, 94087 and 94089, about eight miles from our San Jose base. We troubleshoot carefully, keep safety front and center, and tell you plainly whether a repair is worth it. Below you will find what to try first, how we diagnose a furnace, and the faults we fix most.

Before you call: five minutes of checks

These simple steps sometimes get the heat back on, and if they do not, they help us narrow the problem down.

  • Set the thermostat to Heat, raise the set point a few degrees and replace weak batteries
  • Check that the furnace door panel is fully closed; a safety switch keeps the furnace off if it is not
  • Replace a dirty filter and make sure return grilles are not blocked
  • Confirm the furnace service switch, which often looks like a light switch, is on
  • Look for a blinking status light through the viewing window and note the pattern

How we diagnose a furnace

A gas furnace starts in a fixed order. The thermostat calls for heat, the inducer motor clears the vent, a pressure switch confirms draft, the igniter heats up, the gas valve opens, the flame sensor proves the flame, and finally the blower starts. When something fails, the furnace stops at that step, and often flashes a code.

We watch that sequence from start to finish and use meters to test the component where it stops. That approach avoids guessing and replacing parts that are not the problem. It also helps spot problems that are developing, like an inducer motor that is getting noisy or a capacitor that is weakening.

Repairs we handle most often

The ignition system causes a large share of winter calls. Hot surface igniters are brittle and crack after many heat cycles, and a cracked igniter means the burners will not light. Flame sensors build up a light coating that keeps the control board from recognizing the flame, so the furnace lights and then shuts off seconds later. A careful cleaning often solves it; a worn sensor gets replaced.

Draft problems are next. Pressure switches fail, the tubing connecting them cracks, or the vent gets partly blocked. Inducer motors wear out and start to rattle or hum. On the air side, limit switches trip when a clogged filter or undersized return lets the heat exchanger overheat, and blower motors or their capacitors fail after years of service.

Garage and closet furnaces: a safety note

A furnace in a garage or closet needs combustion air and clear space around it. Stored items, laundry or paint cans near the burners are both a fire risk and a cause of poor combustion. Vent pipes in older homes can separate or corrode where nobody can see them. On every repair, we check the vent connection, look at the flame and inspect what we can see of the heat exchanger. If you ever smell gas, leave the house and call the gas utility from outside.

Repair, replace and the regional rules

A furnace in good overall condition with one failed part is almost always worth repairing. The Bay Area Air District appliance rules do not require replacing working equipment; they apply only when a furnace fails or is replaced. If your furnace is near the end of its life, it is worth knowing that under Rule 9-4, gas furnaces manufactured from 2029 must meet a zero-NOx standard, which points future replacements toward heat pumps. If we find a cracked heat exchanger or a furnace with repeated major failures, we will explain the options and let you decide.

We repair furnaces across Sunnyvale and in Mountain View, Santa Clara, Los Altos, Cupertino and Los Altos Hills.

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What to expect

How a visit goes

  1. Measure first

    Temperatures, pressures, electrical readings and airflow come before any recommendation, so the fix addresses the actual fault.

  2. Show and explain

    We point out failed parts or readings, describe what they mean, and answer questions until the choice makes sense to you.

  3. Respect the home

    Floor protection, careful attic and closet work, and a cleaned-up space before we leave are standard on every visit.

FAQ

Common questions

Don’t see your question? Call (669) 201-9530 and we’ll talk it through.

Why does my furnace light and then shut off after a few seconds?

A dirty or worn flame sensor is the most common cause. Venting or gas supply problems can also produce this pattern.

What does the blinking light on my furnace mean?

It is a fault code. The pattern usually matches a chart on the furnace door. We use it as a starting point and then test the part.

My furnace makes a loud humming or rattling sound when it starts. Is that serious?

It often points to a worn inducer motor. It should be checked before it fails and leaves you without heat.

Is it okay to store things next to my garage furnace?

Keep the area around the furnace clear. Stored items can block combustion air and create a fire hazard.

Does the 2029 rule mean I need a new furnace?

No. It applies to furnaces manufactured from 2029. You can keep repairing a working furnace.

Do you serve neighborhoods outside Sunnyvale?

Yes: Mountain View, Santa Clara, Los Altos, Cupertino, Los Altos Hills and San Jose.

Tell us what your system is doing

Describe the symptom and where the equipment is, and we will schedule a visit, diagnose the problem and walk you through your options.

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