Unfortunately, it’s likely that at some point in its lifetime, you’ll experience a problem with your furnace. To help you prepare for when a furnace issue arises, we’ll cover some common furnace issues, including:
– Thermostat malfunction
– Clogged/dirty air filter
– Turning on and off frequently (short-cycling)
– Blowing cold air
– Making noises
Let’s look at each of these common furnace issues in more detail, so you can get a better idea of what causes them and the appropriate solution.
If you need a furnace repair right away or think your furnace may need to be repaired by a professional, reach out to us. We’ve helped Pittsburgh homeowners with hundreds of furnace repairs, so no matter what the issue is, we can help you. Learn more about the furnace repair we offer or…
Furnace Issue #1: Thermostat malfunctioning
Your thermostat controls how often your furnace turns on (i.e. how long your furnace needs to run to adequately heat your home). If there is an issue with your thermostat, it won’t be able to properly communicate with your furnace, which usually results in a furnace that doesn’t adequately heat your home.
Typically, issues with your thermostat are caused by:
- Faulty power source
- Mechanical issues
- Wiring issues
- Improper placement (thermostats that are placed too close to supply vents can results in inaccurate temperature readings)
Unfortunately, if you have an issue with your thermostat, you’ll probably need a professional to come to repair, replace or move it.
Furnace Issue #2: Clogged or dirty air filter
Clogged and dirty air filters can cause many issues for your furnace. Fortunately, replacing a dirty air filter is an easy (and inexpensive) fix.
To check your air filter, simply open your return vent and check your filter. Does it look like the brown filter on the right?
If so, it’s time to replace your filter. Going forward, you should check your air filter and replace it every month.
Furnace Issue #3: Turning on and off frequently
If you notice your furnace is turning on and off frequently, you’re likely dealing with an issue called short cycling.
Short cycling is what happens when your furnace turns on and shuts off before it has completed a heating cycle.
Short cycling can result in:
- Increased wear and tear on your system
- Hot and cold spots around your home
- Increased energy bills
- Overall reduced lifespan of your furnace
There are a variety of reasons your furnace can short cycle, including:
- Dirty air filter
- A dirty flame sensor rod
- Clogged condensate line
- Oversized furnace
- Overheating
If your furnace is short cycling, our suggestion would be to check your air filter and replace it if it’s dirty.
If your air filter is not dirty, you’re likely dealing with a more technical issue that a professional will need to come to diagnose and fix.
You can learn more about the specifics of what causes your furnace to short cycle on our blog, “Why Won’t My Furnace Stay On? A Pittsburgh Tech Answers?”
Furnace Issue #4: Blowing cold air
If your furnace is blowing cold air, here’s our suggestion:
- Check your thermostat settings- Ensure that your thermostat FAN is set to AUTO not ON. We know this sounds counter-intuitive, but if the furnace fan is set to ON, it will blow all the time, even when your furnace isn’t producing heated air. You should also ensure that your thermostat is set to HEAT not COOL. We know this sounds obvious, but it can happen sometimes.
- Check your air filter- Dirty air filters are the culprits of a lot of furnace issues, and they can prevent your furnace from producing heated air. If your air filter is too dirty, it can block the flow of air to your heat exchanger (part of your furnace responsible for heating air). If there isn’t enough airflow to the heat exchanger, it can overheat and trip your furnace’s limit switch, shutting off the furnace’s burners…which means no heated air.
- Check your condensate drain- This is only relevant if you have a condensing or high-efficiency furnace. High-efficiency furnaces create condensation, which exits your furnace and home via a condensation drain. If this line is clogged or blocked, the liquid can back up in your system. If too much liquid backs up, it will cause the overflow switch to stop the furnace from running so you don’t experience water damage. You can attempt to unclog your condensate drain by attaching a shop vac to the end of your condensate drain.
If your furnace is still blowing cold air, you’re likely dealing with:
- Pilot light issue (only relevant for gas furnace)
- Gas supply issue (only relevant for gas furnace)
- Air duct issue
…and you’ll need to call a technician to come to diagnose and repair your furnace.
You can learn more about what causes your furnace to blow cold air on our blog, “Why Is My Furnace Blowing Cold Air? A Pittsburgh Tech Answers”
Furnace Issue #5: Making noises
If your furnace is making loud or strange noises, don’t worry, you’re not alone. There are a variety of noises that your furnace can make, but a few of the most common include:
- Banging
- Whistling
- Scraping
If your furnace is making a banging noise, you are probably dealing with an issue called delayed ignition, which only happens with gas furnaces. Delayed ignition occurs when your furnace tries to start up and gas starts flowing to your system but that gas doesn’t ignite right away. If this gas doesn’t ignite, it slowly builds up in your system. When it finally ignites, it creates a mini-explosion in your furnace, which creates a “bang” or “boom” noise. Delayed ignition can be caused by a variety of reasons, but two of the most common are:
- The wrong ratio of gas to air (too much gas or too much air)
- Dirty or restricted pilot light
- Misaligned or dirty burners
If you think your furnace is experiencing delayed ignition, you’ll want to contact a professional to come take a look at your system.
If your furnace is making a whistling noise, you likely have loose or damaged air ducts. If your air ducts are not properly connected or there are small holes in your ducts, they can make a whistling noise when air from your furnace is blown through them. To determine if this is your issue, you’ll need to have a technician come to take a look at your air ducts and repair or replace them if necessary.
If your furnace is making a rattling noise, there is likely a loose part somewhere in your system. Usually, this is just due to wear and tear over time. Loose parts can include:
- Panels
- Bearings
- Fan
- Motor
- Air ducts
- And more
Our suggestion would be to check your furnace panels and tighten them if needed. If this doesn’t stop the rattling noise, you’ll need to contact a professional as the loose part will need to be identified, located and tightened or replaced by an expert.
You can learn more about furnace noises and what they mean in our blog, “Why is My Furnace Making a Loud Noise? A Pittsburgh Tech Answers”
Need a professional to diagnose your furnace issue? Contact Calfo
Have one of the issues listed below? Or have another issue with your furnace that you’d like an expert to take a look at? We can help.
