The short answer
Furnace problems in Los Altos usually come from a dirty flame sensor, a failed hot surface igniter, a stuck pressure switch, a weak inducer motor or a clogged filter tripping the high-limit switch. We fix the fault, check combustion and venting, and test for carbon monoxide before leaving.
Winters in Los Altos are mild by national standards, but the nights from December through February are damp and chilly enough that a furnace that will not light becomes urgent fast. Many homes in 94024 still rely on a gas forced-air furnace tucked into a garage corner, an attic platform, a hall closet or a crawlspace under a ranch house. Some of those furnaces have been running for decades. BayPro Heating & Cooling travels about 12 miles west from San Jose to repair them, with attention to both getting heat back and making sure the appliance is burning safely. Here is what tends to go wrong, what we inspect, and how the Air District rules affect your choices.
Signs your furnace needs attention
Some failures are obvious, like a cold house and a silent furnace. Others are easy to dismiss until they turn into a no-heat call on a cold night. Watch for these:
- The burners light for a few seconds and then shut off, over and over
- You hear the inducer motor start, but the burners never ignite
- A blinking light on the control board that was not there before
- Air from the registers feels lukewarm even after the burners run
- A rattling, squealing or booming noise when the furnace starts
- A burning dust smell that lingers well past the first heating day of the season
- Yellow or flickering flames instead of steady blue ones
What we inspect on a furnace call
A modern furnace runs through a set sequence: thermostat call, inducer motor start, pressure switch proof, igniter warm-up, gas valve opening, flame proof, then blower. When the sequence stops, the control board often records a code. We read that code, then confirm it with meter readings rather than swapping parts on a guess.
Common repairs include cleaning or replacing the flame sensor, replacing a cracked igniter, clearing a blocked condensate trap on high-efficiency furnaces, replacing a failing inducer or blower motor, and correcting a limit switch that trips because a filter or return is choked. On older standing-pilot furnaces we also check the thermocouple and pilot assembly.
Safety checks we do not skip
A furnace that runs is not automatically a furnace that is safe. On every repair we look at the flue and vent connector for gaps, corrosion and proper slope, verify the burners have enough combustion air, and test for carbon monoxide around the appliance. Furnaces in closets and crawlspaces get extra attention, since tight spaces and blocked vents are where problems hide.
When the heat exchanger is accessible we inspect it for cracks or rust-through. If we find a condition that could let combustion gases into the living space, we will explain what we see, show you where possible, and advise against running the furnace until it is resolved. Make sure your home has working CO alarms; that advice applies whether or not you call us.
Old furnaces, ducts and attic heat loss
In many older Los Altos homes the furnace is not the only weak link. Duct runs in attics and crawlspaces can be disconnected, crushed or poorly sealed, so heat escapes before it reaches the rooms. If one bedroom stays cold while the furnace runs fine, we check the duct to that room before blaming the equipment.
Repair, replace, and Rule 9-4
Bay Area Air District Rule 9-4 sets a zero-NOx standard for gas furnaces manufactured from 2029. It does not require you to remove a furnace that still works; the rule applies only when equipment fails or is replaced. So repairing a sound furnace remains a perfectly reasonable choice.
Where it matters is planning. If your furnace is older, has a damaged heat exchanger, or needs repeated repairs, it may be time to look at a heat pump instead of another gas unit. We can give you a clear picture of both paths: what the repair buys you today, and what a replacement would look like. BayREN and local clean energy providers sometimes offer incentives for heat pumps; we check the current offer before quoting it.
More services in Los Altos
- AC Repair in Los Altos
- Heating Repair in Los Altos
- Heat Pump Installation in Los Altos
- AC Installation in Los Altos