A furnace that stops heating in San Leandro usually needs a part, not a new furnace. Igniters, flame sensors, pressure switches, inducer motors and blower motors cause most no-heat calls between November and March, and on a furnace in good condition they are worth fixing. Replacement becomes the answer in three situations: the furnace is unsafe, it is near the end of its life and needs a major repair, or the repairs keep coming.
Safety comes first
Some findings make the decision for you.
A cracked heat exchanger. The heat exchanger is the metal chamber that keeps the burner flame and the combustion gases separate from the air your blower sends through the house. A crack can let those gases, including carbon monoxide, into that air. A crack is not something to patch or seal. On a newer furnace the heat exchanger may still be under the manufacturer’s parts warranty, and replacing just the exchanger can make sense. On an older furnace, replacing the furnace is almost always the responsible choice.
Flame problems. Burner flames should be mostly blue and steady. Yellow, lazy or wavering flames, a yellow pilot on an older furnace, soot around the burners or flames rolling out of the burner area all need a technician’s look before the furnace keeps running.
Carbon monoxide concerns. Every home with a gas furnace should have working CO alarms. If one sounds, get everyone outside and call 911 or your gas utility from there. If you smell gas, leave first and call from outside.
When we repair a furnace, we also look at the flame, the venting and the safety controls, so these problems get caught even when the call was about something else.
Age and life expectancy
Gas furnaces typically last 15 to 20 years; electric furnaces typically last 20 to 30. As a rule of thumb:
- Under 15 years with a minor problem: repair.
- Over 20 years, or with a cracked heat exchanger: replace.
- Between 15 and 20 years: it depends on the repair. An igniter or a flame sensor is still a sensible fix. A blower motor, a control board or an inducer motor on a furnace this age deserves a side-by-side comparison with a new one.
Repair history and repair cost
A furnace that needs frequent repairs is telling you something. If you have spent significant money on it in the past two years, that money could have gone toward a new, more efficient system. The common rule of thumb is the same one used for air conditioners: when a single repair costs more than half the price of a replacement, replacement usually makes more sense. You get the repair price before any work starts, so you can make that comparison with real numbers. Typical prices for the common repairs are in our furnace repair cost guide.
Energy bills and efficiency
Standard furnaces are rated at 80% AFUE, and many older units are lower. Condensing furnaces reach roughly 90 to 98%. Going from 80% to 95% means burning about a sixth less gas for the same heat. That is a real saving, but keep the climate in mind: heating here runs mostly from November to March and winters are mild, so the savings are smaller than in a cold climate. Rising bills on an old furnace are a good reason to compare options, not an automatic reason to replace.
A condensing furnace also needs different venting, usually plastic pipe through a wall or the roof, and a drain for the water it produces. In a hall closet or garage that was set up for an 80% furnace, that can mean extra work, and it belongs in the quote.
Common furnace problems: repair or replace?
| Problem | Typical fix | Usually |
|---|---|---|
| Burners never light | Igniter replacement | Repair |
| Lights, then shuts off after a few seconds | Flame sensor cleaning or replacement | Repair |
| Inducer hums, furnace will not light | Pressure switch, hose or inducer motor | Repair |
| Burners run, little air from the vents | Blower motor or its capacitor | Repair, unless the furnace is near the end of its life |
| No response, error codes | Control board | Repair on a younger furnace; compare on an older one |
| Short-cycling, overheating | Dirty filter, blocked return or crushed duct | Fix the airflow |
| Crack in the heat exchanger | Exchanger or furnace replacement | Replace on an older furnace |
Several of these have nothing to do with the furnace’s age. A clogged filter or a crushed attic duct can make a healthy furnace overheat and shut itself off, so the airflow gets fixed before anyone talks about new equipment. If your furnace is not heating right now, start with furnace not heating or book furnace repair.
If you replace
Replacing a furnace in a San Leandro, San Lorenzo or Castro Valley home usually means choosing between three paths:
- A standard 80% furnace. It fits most existing closet and garage installations with the least change.
- A condensing furnace. It burns less gas but needs new venting and a condensate drain.
- A heat pump. It heats and cools from one system. If your air conditioner is also old, or you have no AC and would like it, this is worth a look; see heat pump installation.
Whichever you choose, the size should come from a load calculation for your home, not from the label on the old furnace, and the ducts should be checked at the same time. Furnace installation explains how we handle the job, and financing is available for installations and replacements.
Keep the next furnace longer
Most of what ends a furnace early, such as dirty filters, overheating from poor airflow and neglected flame sensors, shows up at a yearly furnace tune-up before the first cold night. For the cooling side, the same decision is covered in AC repair vs replacement.