If you leave your air filter in your furnace for too long, it can eventually get so dirty that the unit stops working completely. You should change your filter every month. After a while, it becomes clogged.
Of course, it takes a while before a dirty filter causes the furnace to shut off completely. And, you’ll notice plenty of warning signs before it happens.
So, we’re going through all that in this article. We’ll explain:
- Why a Dirty Air Filter Makes A Furnace Stop Working
- Why You Need To Change Your Filter Every Month
- Warning Signs Your Filter Needs To Replacement
- When To Consider Upgrading Your Air Filters
And, call or email us if you have any questions along the way about the furnace in your Havertown, PA home. 
Why a Dirty Air Filter Makes A Furnace Stop Working
A dirty air filter prevents air from flowing from your house into the furnace. Once that happens, the system shuts down because it realizes that something’s wrong. It turns off rather than let any of the components get burned out or otherwise break when it’s not working the way it should.
Even when the filter, or screen, is working precisely as it should, it will weaken the air circulation in your house a little.
That’s always the byproduct of its task: Block dust and other tiny particles from coming through the ducts and getting into the furnace.
But, your system accounts for the cloth screen. It works without a problem — until the cloth gets blocked up.
Over time, the screen gets filled with dirt and dust. After a while, it prevents too much air from getting through. When the circulation gets weak enough, the system can’t work right. That trips the failsafe to shut it down. 
Why You Need To Change Your Filter Every Month
We’ve seen some advice out there recommending a new filter once a season or every 12 weeks. Our advice is to change it out every month. They’re inexpensive — each one is usually less than $10 — and only takes a minute.
The reason is simple: The more often you change it, the less dust that builds upon yours. And, less debris means better airflow and better performance from your HVAC system.
This strategy would seem like a lot if it weren’t cheap and easy to do. You can get a pack of three from any hardware store and be all set for a season.
Then, all it takes is sliding the old one out and sliding the new one in. There’s nothing to take apart or install. You don’t even need to unfasten or unscrew anything. Furnaces are made to make this process very easy.
One quick tip: You’ll see arrows on the cardboard frame around the screen. Those should point into your furnace, not away from it.
The arrows show the direction the air should flow. Remember: air is coming in from the ductwork and entering the furnace. So, align the filter along with that path.
Three Warning Signs Your Furnace Filter Needs Replacement
You can pick up on a few signs that it’s time to replace the filter even before the furnace shuts down completely. If you notice them, change the screen because you can end up damaging the heater beyond repair if you leave it for too long. Three big signs are:
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More Dust In The House
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Weak Air Circulation
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Furnace Short-Cycles
More Dust In The House
If the screen is full of dust, then it can’t hold anymore. But, the dirt and debris coming in through the return vent has to go somewhere! If it can’t stick to the screen, it will blow around and eventually come back out through a vent. 
When that happens, you may notice an increase of dust in the house. That’s because it’s all settling inside the ductwork. Then, it blows back out when the heater clicks on.
Weak Air Circulation
As we mentioned, weak air circulation is the step before a furnace shutting down. You may notice not as much air coming through the vents. Or, the top floor of your home is colder than you want it in the winter — or too hot in the summer if you have central air.
It’s most noticeable upstairs because the system naturally loses some pressure the further you get from the heater itself. A clogged filter makes this even more pronounced.
Furnace Short-Cycles
This is the big one to watch for: Your heater turns on, then turns right back off again. It runs for a minute or even less and then repeats the whole thing a few times every hour. This is called short-cycling, and it’s a huge red flag.
The inside of the unit is overheating. Furnaces generate and spread heat, not house it.
As a result, you may also notice cool air coming through the vents in the winter. That’s the system trying to cool itself back down.
When there’s a backup somewhere — and a clogged screen is a common culprit — the system shuts off quickly. But, the thermostat still tells it to turn on and heat the house. So, it all happens over again.
Meanwhile, all those rapid temperature changes can weaken the inner components. That’s what often leads to a breakdown.
So, if you notice this happening, change the filter right away. Then, call a professional if that doesn’t fix things. You want to get to the bottom of the problem before it gets much worse.
When To Consider Upgrading Your Air Filters
We’ll make one more point about filters because this can increase your home comfort and indoor air quality — or make things worse for your system. 
You can upgrade to a stronger filter if you want to address problems such as pollen and dander in your home. But, the stronger the filter, the weaker the air circulation becomes.
So, check the MERV rating of the screen you’re considering against what your furnace can handle. You’ll find that information in the manual or online. Or, call your HVAC tech if you’re unsure. 
HVAC Repair And Maintenance In Havertown, PA
Changing your furnace filter is an inexpensive and easy way to help maintain your furnace. But, it’s often just the starting point. If you need a tune-up, or if you’re noticing any problems with the heating in your Havertown, PA home, call or email John Cipollone.