Most furnace repairs in San Jose cost $150 to $500, and a typical bill is about $300. On a gas furnace, the price usually comes down to one question: at which step does the furnace stop? When the thermostat calls for heat, the inducer fan starts, a pressure switch confirms the vent is clear, the ignitor glows, the gas valve opens and the flame sensor proves the burners are lit. A little later the blower starts sending warm air through the ducts. Each step has its own part, and each part has its own price.
Prices by repair
| Repair | Typical price | What the furnace does |
|---|---|---|
| Flame sensor cleaning or replacement | $100–$250 | Burners light, then shut off after a few seconds; it retries, then locks out |
| Ignitor replacement | $150–$300 | Inducer runs, the ignitor never glows, no flame |
| Blower motor repair | $250–$500 | Burners run, but little or no air reaches the vents |
| Gas valve replacement | $300–$600 | Ignitor glows, the burners never light |
| Control board replacement | $400–$700 | Nothing starts, or the board fails after the other parts test good |
Gas valves and control boards can run past $500, which is why the headline range describes most repairs rather than every repair. Before a valve is replaced, the gas supply to the furnace is checked. Before a board is replaced, the parts it controls are tested, because a new board is an expensive way to fix a bad ignitor.
What moves the price
The repair itself. By far the biggest factor, as the table shows.
Gas or electric. Electric furnaces have no burners, flame sensor or gas valve. Their usual failures are heating elements, the relays or sequencers that switch them on in stages, and limit switches. They are priced the same way: tested first, priced before work.
Part availability. Common ignitors and flame sensors are on the truck. A board for an older or less common furnace may have to be ordered.
Age of the furnace. Older furnaces often take universal parts that need more fitting, and worn parts tend to show up in pairs.
Where it sits. A furnace in a garage or hall closet is quicker to work on than one tucked into an attic.
Heat exchanger: when price is not the main question
The heat exchanger keeps combustion gases, including carbon monoxide, out of the air that circulates through your rooms. Replacing one typically costs $1,500 to $3,000, if the part is still available for that furnace. A cracked heat exchanger is a safety problem: the furnace stays off until it is resolved. Because the finding is both serious and expensive, it is reasonable to get a second opinion and to ask to see the crack on camera or in a photo. Check your paperwork too: the heat exchanger often carries a longer manufacturer warranty than other parts, though labor is usually not included.
Never ignore a carbon monoxide alarm: get everyone out and call 911 from outside. If you smell gas, leave without touching switches and call the gas utility or 911 once you are out.
What to tell us when you call
A few details help the technician arrive with the right parts:
- What happens after the thermostat calls for heat. Does a fan start? Does something glow? Do the burners light and then go out?
- The blink pattern of the status light, which many furnaces show through a small window in the lower door.
- The brand and approximate age, from the label inside the door.
- Whether a carbon monoxide alarm has gone off.
Getting a firm price
The technician tests the furnace, shows you what failed and gives you the repair price before any work, with no hidden fees. If you go ahead, the diagnostic fee is waived. If replacement turns out to be the better choice, the estimate for a new furnace is free. Same-day service is available for most calls received before noon, and urgent calls are taken 24/7.
When repair stops making sense
- The heat exchanger is cracked on a furnace that is no longer young.
- The repair would cost more than half the price of a new furnace.
- It is the second significant repair in two winters on an older furnace.
- The furnace is old and inefficient and the air conditioner is near the end too. A newer, more efficient furnace burns less gas for the same heat, and one heat pump can replace both systems at once. See furnace installation for the like-for-like route.
A note for San Jose homes
Furnaces here sit idle from spring through fall. Dust settles on the burners and the flame sensor, and the first cool nights bring a wave of “lights, then shuts off” calls. A fall tune-up cleans the sensor and checks the ignitor before then. In Evergreen, many tract homes still run builder-grade furnaces that are reaching replacement age, and in Blossom Valley some homes still have equipment around 40 years old; on furnaces that age, the repair-or-replace math often favors replacement. If your furnace will not light at all, see furnace not igniting; if it runs but the house stays cold, see furnace not heating.