Most furnaces click on three or four times an hour. When it occurs much more often — especially every few minutes — there’s a problem somewhere. Sometimes, it’s a very easy fix. In other cases, you’ll need a professional.
In this article, we’ll run through the most common causes. And, we’ll note what you can do about each one. If you can fix it yourself, great! If not, we’re here to help.
Snowflake Air serves Idaho towns, including Kuna, Caldwell, Boise, and Eagle, and as far north as McCall, Donnelly, and Cascade.
We have an excellent reputation for fast, reliable work and hundreds of five-star reviews to back that up.
But before you call us, keep reading! You may be able to solve the problem yourself.
First, we’ll talk about why a heater turns on and off. Then, we’ll get into what could be causing it.
What Does It Mean When A Heater Short-Cycles?
Short cycling is when your heater turns on and off every few minutes. Most forced-air systems go through this cycle three or four times per hour. So, a short cycle usually means the warm air can’t circulate properly.
That’s especially the case if you notice a blast of cold air coming through your vents right after the heat switches off.
Here’s the problem: Furnaces heat the air inside them and then push it out. They’re not made to store the heat. When that happens, you end up with a lot of damage.
When hot air backs up, the heater shuts off as a failsafe. That’s why it only runs for a few minutes at a time. It will often send a blast of cold air to cool down any components getting too hot.
Meanwhile, your house isn’t warm! So, the thermostat sends another signal to turn on the heat. Then, the process repeats.
Four Reasons Your Heater Turns On And Off (And What To Do)
Heaters turn on and off (short-cycle) when hot air backs up into them. Four possible causes for this are:
1. The Filter Is Clogged
2. Too Many Vents are Blocked
3. There’s A Thermostat Problem
4. Your Heater Is Too Big For The House
No matter the cause for short-cycling, you need to get it addressed as soon as possible. A furnace that keeps turning on and off can end up with a cracked heat exchanger. When that happens, you’ll likely have no choice but to replace the entire system.
The Filter Is Clogged
If you leave your air filter in for too long, it gets clogged. All that dust and dirt builds up, and eventually, not even air can pass through it.
At that point, your furnace generates heat but has no air pressure to force it out into the ductwork. So, it backs up, and the system shuts off.
What To Do
Change your air filter once a month when you’re using the system, and then every three months when it’s not on. This way, it doesn’t collect so much debris that it clogs.
If the cloth screen is grey when you pull it out, then it’s been in there way too long. With any luck, this solves the problem.
Too Many Vents are Blocked
Your central heating system is designed to work with your ductwork and vents. A right-sized system has just enough pressure to reach every room.
But, blocking off your vents can create a backup of hot air. Too much, and the heat has nowhere to go. So, it builds up in the system, causing a short cycle.
What To Do
Make sure all your vents are open. The only time you should ever close one is when the system isn’t running at all.
Then, give each vent a full square foot of clearance. That means no furniture blocking any of them. That’s enough space for the hot air to escape the way it should.
There’s A Thermostat Problem
A faulty thermostat could be giving your system bad signals. If there’s no blast of cold air along with the short cycling, this could be the issue. The difference is that there’s no heat buildup, so there’s no reason to cool it down.
What To Do
Change the batteries if it’s been a while. Low power can cause problems. Then, compare the temperature readout to another thermometer. If the thermostat has a different temperature, there could be a calibration issue.
Last, gently check all the wires you can see. Make sure everything is secure. After that, however, it’s time to call a professional.
Your Heater Is Too Big For The House
Having an oversized heater causes the same problems as blocked vents: You end up with a lot of heat but nowhere for it to go.
A heater that’s too big will send a powerful blast of hot air into your home. It’s enough so the thermostat sees a sudden temperature rise and shuts off the heater.
But, forced-air systems need to run for 10 or 15 minutes. Otherwise, that short blast will cool down too soon. So, the temp drop right back down, and the thermostat turns on your central heat again.
But, your furnace expects to run for much longer. So, it generates more heat that ends up staying inside the system.
What To Do
The bad news is that the only way to solve this problem is to buy a new furnace. Single-stage furnaces (ones that only turn on or off) don’t give you any other settings. It’s either full blast or nothing at all.
The good news is that this won’t be the case if the short-cycling just started happening. If your furnace is too big, you’ll have noticed this problem all along.
Don’t Ignore A Short-Cycling Heater!
Even if your short-cycling problem just started, it can cause a lot of internal damage to your furnace. All that heat is no good for the components. And, neither are the drastic temperature changes when the system cools itself down.
And, make sure you know the other signs of a broken heater and common furnace noises and what they could mean. Fixing a small problem before it gets bigger saves you money and prevents all sorts of headaches.
Heater Repair In Kuna, ID
If your heater in your Treasure Valley home keeps short cycling, call Snowflake Air right away. We’re the trusted name for furnace repair in Kuna, ID and across the Boise area. You want to get to the bottom of it before this small, inconvenient issue becomes more severe and much more expensive to fix. Click below or call us at (208) 205-9078.