Furnaces keep homes warm and comfortable through the colder months in Bellingham, Ferndale, Lynden, Blaine, and throughout Whatcom County. This FAQ answers common questions about furnace repair, replacement costs, efficiency ratings, maintenance, strange noises, and warning signs that it may be time to call a technician.
If your furnace will not turn on, start by checking the thermostat, circuit breaker, air filter, and furnace power switch. Make sure the thermostat is set to heat, the breaker has not tripped, the filter is not severely clogged, and the furnace switch is on. If those steps do not solve the issue, the problem may involve the ignitor, control board, safety switch, or gas supply and should be checked by a licensed HVAC technician.
A furnace may blow cold air if the thermostat fan is set to “On” instead of “Auto,” the air filter is dirty, the furnace is overheating and shutting off the burner, or the ignition system is not lighting properly. If replacing the filter and checking the thermostat does not fix the issue, it is time to schedule furnace service.
A furnace that turns on and off repeatedly is short cycling. Common causes include a dirty air filter, restricted airflow, an oversized furnace, a faulty flame sensor, thermostat problems, or a blocked exhaust vent. Short cycling puts extra wear on the system and should be addressed before it leads to a more expensive repair.
A brief dusty burning smell when the furnace first runs for the season can be normal as dust burns off the heat exchanger. However, a persistent burning smell, electrical smell, plastic smell, or any odor that returns every cycle should be inspected. If you smell gas, leave the home immediately and contact your gas company or emergency services.
Furnace replacement costs vary based on your home’s size, existing ductwork, venting requirements, efficiency level, electrical needs, permit requirements, and installation complexity. As a general range, standard-efficiency gas furnaces may cost around $4,500–$7,500, high-efficiency gas furnaces may range from about $5,000–$9,500, and premium high-efficiency systems may cost more.
Repair may make sense if your furnace is under 10 years old, the issue is minor, and the rest of the system is in good condition. Replacement may be the better option if the furnace is 15–18 years old or older, needs frequent repairs, has rising operating costs, or has a cracked heat exchanger. A technician can inspect the system and help you compare repair cost, safety, efficiency, and remaining lifespan.
AFUE measures how efficiently a furnace turns fuel into heat. An 80% AFUE furnace uses about 80% of the fuel for heat, while a 95% or 98% AFUE furnace uses more of that fuel and wastes less. High-efficiency furnaces cost more upfront but can lower operating costs over time, especially for homes that rely heavily on heating during the colder months.
A properly maintained gas furnace often lasts around 15–20 years. Annual maintenance, regular filter changes, proper installation, and timely repairs can help extend the life of the system. Furnaces that are neglected, oversized, undersized, or operated with dirty filters may fail sooner.
Some minor popping from ductwork expansion can be normal, but loud banging, booming, scraping, grinding, or rattling should not be ignored. A loud boom at startup may point to delayed ignition, while scraping or grinding can indicate a mechanical issue. If the noise is new, recurring, or getting worse, turn the system off and schedule service.
There are a few safe things you can check yourself, including the thermostat setting, batteries, breaker, air filter, power switch, and condensate drain on high-efficiency furnaces. If the furnace still will not start, the breaker trips again, the system shuts down quickly, or you smell gas, call a licensed technician rather than trying to bypass safety controls.
A cracked heat exchanger is a serious furnace safety issue because it can allow combustion gases, including carbon monoxide, to mix with the air moving through your home. Carbon monoxide is colorless and odorless, so a cracked heat exchanger should never be ignored. If a technician identifies a crack, stop running the furnace and review replacement options.
A dirty furnace filter restricts airflow and forces the system to work harder. Over time, this can increase energy bills, cause overheating, trigger short cycling, strain the blower motor, reduce indoor air quality, and shorten the lifespan of the furnace. Replacing the filter regularly is one of the easiest ways to prevent avoidable furnace problems.
An 18-year-old furnace is near or past the typical replacement window, so a significant repair deserves a closer look. If the system has been well maintained and the repair is minor, repair may still be reasonable. If the furnace has had multiple repairs, rising energy bills, or heat exchanger concerns, replacement is usually the smarter long-term option.
LSM Heating Plumbing Electric provides furnace repair, maintenance, and replacement throughout Bellingham, Ferndale, Lynden, Blaine, and all of Whatcom County. Our team can inspect your furnace, explain your options clearly, and help you decide whether repair or replacement makes the most sense for your home.
