The short answer
Many Los Gatos furnace problems come from simple causes such as clogged filters, dirty flame sensors, failed igniters or blocked vents, but repeated resets and guesswork can make them worse. A technician tests the full ignition and safety sequence, checks venting and carbon monoxide, and explains repair options clearly.
Los Gatos winters are mild by most American standards, but shaded lots under tall trees and homes tucked against the foothills can feel damp and cold on December evenings, and a furnace that refuses to start turns a comfortable house chilly fast. EliteAir Heating & Cooling repairs gas furnaces throughout 95030 and 95032, about 7 miles south of our San Jose base. A lot of furnace trouble gets made worse by well-meant assumptions, so this page starts by clearing up a few common ones, then explains what a professional repair involves and how today's Air District rules affect the repair-or-replace decision.
Five common furnace assumptions, corrected
These come up on service calls all the time, and each one can lead a homeowner in the wrong direction.
- Resetting it a few more times will fix it: repeated resets can mask an ignition or venting fault, and some control boards lock out for an hour after several failed tries
- A brand-new filter cannot cause problems: a filter that is far more restrictive than the blower was designed for can overheat the heat exchanger and trip the limit switch
- If it lights, it is safe: a furnace can light and run while venting poorly or with a cracked heat exchanger, which is why carbon monoxide testing matters
- Closing vents in unused rooms saves energy: closing many registers raises duct pressure and can cause overheating and short cycling
- Cold air at startup means the furnace is broken: many furnaces wait for the heat exchanger to warm before the blower starts, and a brief rush of cool air from the ducts is normal
What actually fails
Once the assumptions are set aside, the real causes tend to be familiar. Flame sensors build up a film and stop proving flame, so the burners shut off after a few seconds. Hot surface igniters crack with age. Draft inducer motors wear out, and pressure switches fail or sense a blocked vent. Blower motors and their capacitors weaken, leaving burners that run with no warm air reaching the rooms. Control boards occasionally fail, often after a power surge.
In older Los Gatos homes, the furnace may sit in a tight closet, an attic or a crawlspace. Those locations collect dust and sometimes rodents, both of which affect airflow and wiring. We check the surroundings along with the furnace itself.
The repair visit, in order
Our technician starts at the thermostat to confirm it is calling for heat, then follows the furnace's own sequence: inducer, pressure switch, igniter, gas valve, flame sensing, blower and limit controls. The board's fault light often narrows the search. Along the way we measure gas pressure, look at burner flame quality and test temperature rise across the heat exchanger.
Every visit includes a venting inspection and a carbon monoxide check around the appliance. If we find a cracked heat exchanger or a serious venting fault, we explain it clearly and, where required for safety, shut the gas off to the furnace until it is corrected.
Repair now, plan for later
Bay Area Air District appliance rules do not require replacing working equipment; they apply only when an existing furnace or water heater fails or is replaced. So repairing a furnace to keep it running is entirely reasonable. Looking ahead, Rule 9-4 requires natural gas furnaces manufactured from 2029 to meet a zero-NOx emission standard, which in practice points homeowners toward heat pumps for replacements after that date.
For an older furnace facing a big repair, we will give you an honest view of what remains in it and what a heat pump would involve in your home. BayREN and your local clean energy provider list current electrification incentives, which change by funding cycle, and we confirm what is available before quoting. The federal 25C credit no longer applies to heat pumps installed after December 31, 2025.
If you smell gas
Do not try to relight the furnace or flip switches. Leave the house, then contact the gas utility from outside. If a carbon monoxide alarm sounds, get everyone out and call emergency services. Once the home is cleared, we can diagnose and repair the furnace.
We repair furnaces in Los Gatos and nearby Monte Sereno, Campbell, Saratoga, Cupertino and Santa Clara.
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