If you have an old furnace that stopped working, a furnace repair call can go one of two ways. Either the fix is straightforward and you’re back up and running, or the technician finds something that is going to cost a lot more and you question whether it’s better to actually replace it.
Most homeowners don’t think about their furnace until it stops working. For some issues, like a failed ignitor or a bad flame sensor, the repair is worth it regardless of the furnace’s age. For others, like a cracked heat exchanger or a failing blower motor on a 15-year-old system, it might actually be better to get a new one.
This article covers the factors that determine whether to repair or replace, common furnace repairs and what they cost, and how to tell when you’re better off putting that money toward a new system.
How Long Do Furnaces Last?
Most furnaces last between 15 and 20 years. Some last longer with consistent maintenance, and some fail earlier due to poor installation or being oversized for the home.
After 15 years, furnaces start to show their age, with parts wearing out, efficiency dropping, and repairs becoming more frequent. A furnace that needed one service call in its first decade might need two or three per year once it passes 15.
This doesn’t mean you need to replace a furnace the moment it reaches 15 years old. A well-maintained system can run reliably for 20 years or more. But if you’re facing a major repair on a furnace in this age range, the expected remaining lifespan becomes a factor in whether that repair makes financial sense.
If you don’t know how old your furnace is, check the label on the unit itself. Most manufacturers print the serial number on a sticker inside the front panel, and the first few digits usually indicate the manufacture date. A serial number starting with 1208, for example, likely means December 2008.
Common Furnace Repairs and Costs
Some furnace repairs cost under $200 and take less than an hour, while others run into the thousands and make you question whether the furnace is worth keeping. Here are some of the most common scenarios we get called for:
Furnace Won’t Ignite
When your furnace won’t light at all, the problem is usually the ignitor or the flame sensor. The ignitor lights the burners each time the furnace cycles on, and it wears out over time. Replacing one typically costs between $150 and $300, and on a furnace under 15 years old, this repair almost always makes sense.
The flame sensor detects whether the burners are lit and shuts off gas flow if they’re not. A dirty or failed sensor can prevent ignition entirely, and since the repair runs $100 to $250, it’s worth doing on almost any furnace that still has some life left in it.
If the ignitor and flame sensor check out, the issue might be the gas valve, which controls fuel flow to the burners. Gas valve replacement costs between $400 and $800, and at that price point, the age of your furnace becomes a factor. On a system under 10 years old, it’s a reasonable repair. On a furnace pushing 18 years, you’re putting money into a system that may only last another year or two.
Furnace Turns On and Off Repeatedly
If your furnace turns on, runs for a few minutes, then shuts off and repeats the cycle, that’s called short cycling. It usually points to a faulty flame sensor, a clogged air filter, or a problem with the circuit board.
Replacing a flame sensor is inexpensive and worth doing, regardless of the furnace’s age. If the circuit board is failing, replacement runs between $500 and $1,200, depending on the furnace model. That kind of repair is reasonable for a 10-year-old system that’s otherwise been reliable, but it’s harder to justify on a furnace that’s already past the 15-year mark and showing other signs of age.
Furnace Runs But No Heat
If the furnace is running but not producing heat, the inducer motor or gas valve may be the cause. The inducer motor pulls combustion gases through the system, and when it fails, the furnace often won’t ignite as a safety precaution.
Replacing an inducer motor can cost between $400 and $700, depending on the part and labor involved. A failed gas valve causes the same symptom and costs $400 to $800 to replace. Both repairs make sense on a furnace that’s still in the first half of its lifespan, but once you’re past 15 years, spending $600 or $700 on a single repair starts to feel like a gamble.
Furnace Not Blowing Air
When you hear the furnace running but no air comes through the vents, the blower motor has likely failed. You might notice grinding or squealing sounds in the days or weeks before it quits completely.
Blower motor replacement costs between $400 and $900, with variable-speed motors on the higher end and single-speed motors on the lower end. On a furnace under 12 years old, this repair is usually worthwhile since you can expect several more years of use from the system. On an older furnace, especially one that’s had other recent repairs, it may make more sense to put that money toward a replacement.
Strange Noises
If you hear a banging, rattling, or squealing sound from your furnace, it is usually a sign of worn or failing parts.
Squealing typically means a blower motor problem. Banging can indicate a delayed ignition, which could be caused by the ignitor or the gas valve. Rattling might be loose ductwork or a failing inducer motor.
The cost to fix depends on the source, but diagnosis usually starts around $100 for a service call, and most technicians can identify the problem quickly once they hear it in person.
Rising Energy Bills
If your heating costs have increased without a rate change or difference in usage, furnace efficiency may be declining. This happens as furnaces age, particularly past 15 years.
There’s no single part to replace to fix this issue. The system is working harder to produce the same amount of heat, and that usually points toward replacement rather than repair.
Yellow or Flickering Flame
A healthy furnace flame burns blue. A yellow or orange flame indicates incomplete combustion, which can produce carbon monoxide. This could be a burner issue, a ventilation problem, or a cracked heat exchanger.
Heat exchanger replacement costs between $1,500 and $3,500, and because that approaches half the price of a new furnace, heat exchanger failure on a system over 10 years old usually means replacement is the better path.
If you suspect carbon monoxide is present, turn off the furnace and have it checked immediately.
When to Repair vs. Replace Your Furnace
There are a few rules HVAC professionals use to help homeowners decide whether a repair makes sense or whether the money is better spent on a new system. Use the rules as a starting point, but factor in the system’s overall condition and how much you’ve already spent to keep it running.
The 15-Year Rule
Furnaces older than 15 years are approaching the end of their reliable lifespan, and major repairs on these systems rarely pay off.
A $700 inducer motor replacement might keep an 8-year-old furnace running for another decade. The same repair on a 17-year-old furnace buys you a year or two at best before something else fails.
The older the system, the less sense it makes to keep putting money into it.
The 50% Rule
If the repair costs more than half the cost of a new furnace, replacement is usually the smarter investment.
In the Greenville area, new furnace installation typically runs between $3,000 and $7,500, depending on the size of the home and the efficiency rating you choose. That means a repair estimate north of $1,500 on the low end, or $3,500 on the high end, starts crossing into replacement territory.
At that point, you’re better off putting the money toward a system that will last another 15 to 20 years rather than extending the life of one that’s already on its way out.
The $5,000 Rule
Multiply your furnace’s age by the repair cost. If the result is over $5,000, lean toward replacement.
A 10-year-old furnace needing a $400 repair comes out to $4,000, which favors repair. A 14-year-old furnace needing a $500 repair comes out to $7,000, which favors replacement.
This rule accounts for both the repair cost and the remaining life of the furnace.
Warning Signs Your Furnace Is Failing
Some furnace problems are one-time repairs. Others are signs that the system is wearing out, and replacement is coming whether you want it or not.
- Age over 15 years. A furnace past 15 years isn’t necessarily failing, but it’s entered the window where failures become more likely. If your furnace is in this range and you’re seeing other signs on this list, it’s worth getting a replacement quote even if the system is still running.
- Frequent repairs. One repair every few years is normal. Two or three repairs in a single heating season is a pattern. Add up what you’ve spent over the past two years. If it’s approaching the cost of a new system, you’re likely better off replacing.
- Rising energy bills. Furnaces lose efficiency as they age. If your heating costs have climbed over the past few winters without a rate increase or change in usage, the furnace is working harder to produce the same amount of heat. This is a gradual decline, not something a single repair can fix.
- Uneven heating. If some rooms are warm while others stay cold, the furnace may be struggling to distribute heat effectively. This can be a ductwork issue, but on older furnaces it often means the system no longer has the output it once did.
- Strange noises. Occasional clicks and hums are normal. Banging, popping, rattling, or squealing are not. These sounds usually indicate worn components, and on older furnaces they often come in clusters. You fix one noise and another appears a few months later.
- Yellow or flickering burner flame. A furnace flame should burn steady and blue. Yellow or orange flames indicate incomplete combustion, which can mean a cracked heat exchanger. This is a safety issue because it can leak carbon monoxide into your home. If you see a yellow flame, get it inspected before running the furnace again.
- Visible rust or cracks. Rust on the furnace indicates moisture problems that lead to further corrosion and part failures. Cracks, especially on or around the heat exchanger, are a safety concern and typically mean the furnace needs to be replaced.
- The furnace runs constantly. If your furnace runs nonstop but your home never reaches the set temperature, the system is struggling to keep up. On older furnaces, this usually signals that replacement is the better path.
Safety Concerns That Mean Immediate Replacement
Most furnace problems are inconvenient, but a few can be dangerous. If you’re dealing with any of the following, don’t wait for a repair estimate.
Cracked Heat Exchanger
The heat exchanger separates the combustion process from the air circulating through your home. When it cracks, carbon monoxide can leak into your living space. Symptoms of carbon monoxide exposure include headaches, dizziness, nausea, and confusion. At high levels, it can be fatal.
If a technician diagnoses a cracked heat exchanger, replacement is the only safe option. The part itself costs $1,500 to $3,500 to replace, and on a furnace over 10 years old, that money is better spent on a new system.
Gas Smell
If you smell rotten eggs or sulfur near your furnace, you may have a gas leak. Natural gas is odorless, but utility companies add a chemical called mercaptan to make leaks detectable.
If you smell gas, turn off the furnace, leave the house, and call your gas company or 911. Do not flip light switches or use anything that could create a spark. A gas leak isn’t something to diagnose yourself.
Carbon Monoxide Detector Alerts
If your carbon monoxide detector goes off, take it seriously. Leave the house immediately and call 911. Don’t re-enter until emergency services have cleared the home.
A furnace producing carbon monoxide needs to be inspected before it runs again, and depending on the cause, replacement may be the only safe solution.
Repeated Pilot Light or Ignition Failures
Occasional ignition issues can be fixed with a new ignitor or flame sensor. But if the furnace repeatedly fails to ignite or the pilot light keeps going out, there may be a deeper issue with gas flow, venting, or the combustion system.
These problems can lead to gas buildup or incomplete combustion, both of which are dangerous. Get it inspected before continuing to use the furnace.
Contact A Furnace Professional
A furnace might fall on the repair side for some factors and the replacement side for others. When that happens, weigh the safety issues first, then the financial factors. If you’re spending more time thinking about the furnace than using it, that’s usually a sign it’s time for a new one.
At Air Today Heating & Cooling, we’re here to help you make the best decision for your home. Whether that means repairing your current system or helping you select a new, efficient furnace, our team of Greenville HVAC experts is just a call away. Contact us online or call us today at 864-295-0905!