Furnace Repair in San Jose

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San Jose winters are mild by national standards, which is exactly why furnace problems catch people out. A heater that sits unused from March to November can develop a dirty flame sensor, a failing igniter or a cracked belt without anyone noticing, and then refuse to start on the first cold, damp night in December. This page covers heating repair with a safety-first view, because a gas appliance deserves more caution than an air conditioner.

Cool Aid Air Conditioning & Refrigeration is a family-owned HVAC company founded in 1966 and based in Santa Clara, next to San Jose. Our technicians are licensed under CA C-20 and repair the gas furnaces most San Jose homes rely on. The rest of our city services are on the San Jose HVAC and refrigeration hub.

Safety comes first with gas heat

Other warning signs that mean you should shut the furnace off and call a technician rather than keep resetting it:

• A carbon monoxide alarm sounding, or headaches and nausea that ease when you leave the house.
• Soot around the furnace or registers, or a lazy yellow flame where it should be blue.
• A burning or electrical smell that does not fade after the first few minutes of the season.
• Scorch marks near the burner area or on the cabinet.

A working carbon monoxide alarm near the bedrooms is worth testing before every heating season.

The furnace faults we see most in San Jose homes

No heat at all

Often an ignition problem: a worn hot surface igniter, a dirty flame sensor that shuts the burners off after a few seconds, or a pressure switch that does not prove the draft. We test each part rather than replacing them in turn.

Blowing cold air

The blower is running but the burners are not, or they are cutting out. Causes range from a thermostat set to Fan On to an overheating furnace that trips its limit switch because the filter is blocked.

Short cycling and uneven rooms

A furnace that fires, shuts off and fires again is often overheating or struggling with restricted airflow. In older homes around Willow Glen and Rose Garden, where ducts may be decades old, leaky or crushed runs can leave back bedrooms cold even when the furnace itself is healthy.

Noises and smells

Squealing usually points to a blower motor or belt, rumbling after shutdown to burner issues, and a dusty smell at start-up is normal for a few minutes after months off.

Wildfire smoke seasons matter here as well. A filter that loaded up with smoke in late summer can still be in the furnace in December, restricting airflow enough to trip the high limit. Check it before the first cold night, and keep a spare filter on hand, because a smoky autumn can load a new filter within weeks. If you are not sure which filter your furnace takes, the size is printed on the edge of the old one.

Older and unusual heaters

San Jose has a wide mix of housing. Historic homes near Naglee Park and older bungalows across Downtown and East San Jose sometimes still have wall heaters or floor furnaces, while newer builds in Evergreen typically have a forced-air furnace in the attic or garage. We work on wall heaters and floor furnaces as well as standard forced-air units. With older heaters, we will be direct about condition and safety, since age alone can make a unit hard to keep running safely.

How a repair visit works

• We start with the thermostat and power, including the furnace service switch that is easy to knock off.
• We watch a full ignition sequence and read the furnace's fault codes if it has them.
• We test igniter, flame sensor, pressure switch, limit switches and blower with meters.
• We check venting and look for signs of combustion problems.
• You get a clear explanation and your options before any repair begins.

Every repair is backed by our 1-year parts and labor warranty. For our general approach to residential repairs, see residential HVAC repair services, and for seasonal checklists and warning signs, our furnace and heating guide for Bay Area homes.

Repair, replace, or go electric?

When a furnace is old and the repair is major, it is worth comparing options. Our San Jose furnace repair vs replacement guide walks through the decision. Replacing a furnace in a San Jose single-family home or duplex generally needs a city mechanical permit (City of San José). If you are replacing it anyway, a heat pump can take over both heating and cooling, and the city's community electricity provider offers a rebate for that switch; see heat pump installation in San Jose. A pre-winter tune-up is the simplest way to avoid the December no-heat call altogether, covered on our San Jose HVAC maintenance page, and if heat fails at night with vulnerable people at home, our emergency HVAC repair service is available 24/7.

Schedule a furnace repair in San Jose

Frequently asked questions

Written and reviewed by Jim McKinny, owner of Cool Aid Air Conditioning & Refrigeration — California C-20 and C-38 licensed, EPA Universal certified, second generation of a family business serving the Bay Area since 1966. Every job we complete is backed by our 1-year parts & labor warranty.