Imagine that it’s the middle of winter. Suddenly, your house goes from being toasty to becoming an icebox. After ruling out a power outage, you conclude that your furnace has stopped working. This guide will tell you what went wrong and how to fix it!
The Basics
First, make sure that anyone you contact for repair can handle your furnace. Some brands may require special treatment.
Second, many modern furnaces have a LED light that blinks red or green. Before you start repairing, write down what that LED light is doing. The light will blink in a code indicating the problem. Record this before turning the power off.
Let’s look at what could be going wrong and what you can do about the problem. Even if you call a repair service, a professional will appreciate the steps that you have already taken towards solving the problem.
Diagnosing the Symptoms
Below are the 5 most common furnace problems and how to fix them if you want to DIY. Please remember to record the error code and turn your furnace off before attempting repairs. It is also important to understand that furnace parts can wear out and get dirty just like anything else. This video by John Holland from All Utah Home Repair Services has a quick guide to basic furnace maintenance.
Dirty Flame Sensor
If your furnace turns on for about three seconds, then shuts off, you probably have a dirty flame sensor. This is the most common problem and also one of the easiest to fix. The sensor will be located near the burners, usually opposite the ignitor. It is usually a metal rod. If this rod cannot sense the flame, it will shut the furnace off. Locating, inspecting, and cleaning the rod only requires a cleaning pad.
Beware if your furnace restarts too many times; it will lock itself for three hours. Your furnace is not dead if this happens!
Replace the Furnace Filter
If your furnace does not produce enough heat, it may be time to replace your filter. Your furnace may also turn off because it doesn’t have adequate air circulation. The symptoms are similar to the dirty flame sensor problem, but the solution is different.
Broken Thermostat
If your furnace heats or cools your house at random, or is way too loud, a broken thermostat is probably the culprit. The furnace has stopped regulating both your house and its internal heat. This problem could be as simple as a dead battery, or you may need to replace the thermostat.
Bad Motors
If you turn your furnace on and nothing happens, the most likely issue is a faulty inducer motor. If you put your hand on the inducer motor and it feels hot, it is probably the problem. Your furnace may have a diagram for this part; please refer to that when trying to fix this part. More likely than not, something is stuck inside the motor’s blower wheel. If you do need to replace it, the motor might cost $100–400, but installation services may raise that to $650.
If you smell burnt plastic, the problem is probably a bad blower motor. Your blower motor may also be hot to the touch. Unfortunately, the only way to fix a bad blower motor is to replace it. A standard blower motor may cost $600–700 to replace.
Faulty Control Board
This is the epitome of “technical difficulties.” The only way to repair a faulty control board is to get a new one, which will cost around $300 to $650 with additional labor charges. Note the brand and model of your furnace.
If your furnace issue doesn’t match any of these, you can continue looking for your issue online or seek professional assistance.
Repair or DIY?
If your problem goes beyond DIY, you may need to ask a professional. LocalProBook will help you find the right repairperson. A repair costs from $260–$2,500 depending on the damage. It’s important to weigh whatever quote you get against getting a new furnace entirely.
What If I Need a New Furnace?
If your furnace cannot be repaired, you must buy a new one. Including labor and installation, this can range from $3,000 to $7,600. The three most common brands are American Standard ($1,600–$6,000), Bryant (~$2,300), and Carrier (~$6,300).
Consider the following when buying a new furnace:
* Size. The size of your house affects what kind of furnace you will need.
* Efficiency. Furnaces have gotten more efficient over time. If saving energy is a concern for you, it may be more expensive and/or risky to buy a newer model, but it could also save you money over time.
* Warranty. Your furnace should come with a warranty. Always read the fine print.
* Air quality. If you have allergies or asthma, getting a furnace with good air filtration is critical.
* Technology. A good UI can help maintain your furnace without needing to call anybody!
This video featuring Bryan of Fire & Ice Heating and Air Conditioning, Inc. in central Ohio covers most of the points that will help you decide if you should repair your current furnace or buy a new unit. A new furnace is a big investment that should serve you for years.
Alternatively, you may want to consider a heat pump. Although more expensive to install ($4,900–$12,000), heat pumps can save you money throughout the year and have no risk of gas leaks.
Conclusion
If you have a furnace issue, the first thing you should do is stay calm. The next thing is recording the brand and light patterns. Then turn the furnace off so you can inspect it safely and decide if you want to attempt fixing it or call a professional. Even if you ask a professional instead of fixing the furnace yourself, they will appreciate your knowledge and initiative.
Frequently Asked Questions (FAQ)
What is the advantage of a 2-stage furnace?
When a proper heat load calculation is done it will give you the proper furnace size for the coldest day of the year minus some extreme temperatures. When it is not the coldest day of the year your furnace will be too large and cycle more than it should which will be less comfortable and less energy efficient. A two stage furnace on low stage will provide approximately 60% of the heat as high stage so it will stay on longer and provide more even heating. This however is only as good as the control telling it what to do. Many thermostats unfortunately keep it in high stage too long negating the advantages. A two stage furnace is like having a small and large furnace in one.
What size of furnace do I need for a 1,000 sq. ft. house?
That is impossible to answer with the information you have given. First thing that is needed is indoor and outdoor design temperature. Second thing is how many square feet of each different kind of building material. How many square feet the ceiling, floor, walls, windows and doors there are. That is where the heat is lost from. The square footage of a home could only be used to calculate heat load if every home was built in the same climate with the same material and the same construction type.
How can you add air conditioning to an existing furnace?
The furnace is simply an air handler when asking for cooling. You would need to install a cooling coil at the outlet of the furnace. Install a condensate line from the new cooling coil. Install a condensing unit outside. Install refrigerant lines between the cooling and condensing coils. Install electricity to the condenser. The existing duct work will need to be sized to make sure it is large enough. Many places require larger ducts for cooling depending on the heating and cooling loads where you live. The furnace may not have a large enough blower for the required air flow so it may need to be replaced anyway. A full heat load calculation should be done to ensure the furnace and air conditioner are properly sized. A duct calculation should also be done to make sure the ducts are properly sized.
What do you think of Amana for gas furnaces vs Lennox?
Especially at the lower price points they are basically the same. At the top price points one may have more favorable features than the other. Two gripes I have always had about Lennox is they tend to try and reinvent the wheel in an attempt at market distinction. This results in more brand specific parts and more hassle with repairs later. The other issue I have had , and this is more based on where I am, it is difficult getting those proprietary parts. With most other brands I can get the parts locally. All of the larger brands will have a builder model all the way up to variable speed high efficiency furnaces and everything in between so focus on the features you want.
However the brand should really be your least concern. A good contractor can make any furnace operate great and reliably. A bad contractor can make even the most expensive furnace seem like a piece of junk. Put most of your effort into finding a good contractor and then go with the brand they are selling.
Is there any reason my furnace filter hasn’t been changed in 2 years?
You would be the best one to answer that since it would be your responsibility. It is however not unusual to be able to go 2 years or more under certain circumstances. The only way to tell for sure is to measure the resistance. Most people just look at and take a guess though.
How do I dispose of gas furnace filters? Can I recycle? So big to put in garbage bags.
Put them in the garbage can, bending works. They are not readily recyclable although just about anything is recyclable with enough effort. When I change filters here at work I time it with garbage pickup because I fill an entire Dumpster with them.
Why is it not a good practice to install a natural gas heater in the attic vs a basement or small closet space?
It is an excellent practice, at least where I live. Most furnaces are either in closets or attics. Older homes they are often in crawl spaces because they were gravity heaters and heat rises. The only reason I could think of not to put them in attics would be who would want to service them when it is 110 outside? Here it seldom gets even above 85 degrees so it isn’t so bad servicing them in summer.
Greg Kummer answered your questions (Greg Kummer profile on quora)
Expertise: 30+ years factory trained HVAC technician.
Education: AOS in Refrigeration & Air Conditioning, Universal Technical Institute (UTI)
Location: Lives in Santa Barbara, CA
Title: Mechanical Systems Lead (from 2015 - present )