Turn It Off and on Again Response Unit
If you lot detect that your furnace blower is turning on and off when it shouldn't, y'all'll desire to accept that checked as soon as possible. Not just does this decrease your comfort, it tin damage your furnace.
So what'due south causing this? Well, it depends on your state of affairs.
Is your blower turning on/off constantly during a heating wheel? If then, information technology'southward most likely caused by
- Poor duct design
- Abnormally common cold temperatures entering the rut exchanger
- Abnormally hot temperatures in the estrus exchanger
Is your blower turning on/off when your furnace isn't heating? If so, it's near probable caused past a bad fan limit switch.
We'll become over what you lot tin do on your own to solve your trouble and when yous'll need a professional.
But first, permit's take a quick look at how your furnace blower works in normal operation to determine whether you lot actually have a problem or not.
How your furnace blower usually works
In normal operation, your furnace blower fan should come on 1.five to three minutes after your thermostat calls for estrus and should turn off several minutes after the heating cycle ends.
Your blower should run constantly until the heating bike ends.
When your furnace isn't actually heating, though, your furnace blower shouldn't exist running at all.
And then, if your blower is turning on/off during a heating cycle or later on the call for heat stops, you accept a trouble.
Now, let's look at what'south causing your blower to "misbehave" in both of these situations…
If your blower is constantly turning on/off during a heat bicycle…
...you take one of these 4 problems:
- Ductwork that is leaky or designed poorly
- A furnace that is oversized for the dwelling house
- Abnormally low temperatures in the heat exchanger
- Abnormally high temperatures in the estrus exchanger
So, what tin can you practice to stop your blower from constantly turning on and off during a heat bicycle?
Unfortunately, you'll need a professional person to solve most of the bug listed higher up. But earlier you phone call a professional person, two things you can practise to try and solve the problem are:
one. Cheque for a dirty air filter and replace if needed. A clogged filter limits the corporeality of cool air that passes over the heat exchanger, causing it to overheat and shut off. At the same fourth dimension, your blower turns on to help absurd it down. Equally soon equally the heat exchanger cools downward, though, the burners turn dorsum on (because the thermostat is still calling for heat) and the process repeats.
And then, if your air filter looks similar the one to the right, supplant it immediately and see if that fixes the problem.
2. Check for a dirty air handler blower fan. Similar to a clogged filter, dirt on the blades of the air handler fan will decrease cold airflow over the rut exchangers, resulting in the aforementioned blower on/blower off design. And then, if your air handler looks like the one below, effort wiping the blades advisedly with a dry towel or toothbrush.
If y'all're still noticing that your blower turns on and off constantly during a heat cycle, you'll need to take a professional inspect your unit to find the problem and correct it.
If your blower is constantly turning on/off when the furnace isn't heating…
...you lot virtually likely accept a bad fan limit switch.
Your furnace fan limit switch is basically a control system that determines when the furnace blower assembly should plough on and off. The system uses a "temperature probe" to detect temperature changes inside the heat exchanger (see epitome below) and turns your blower on and off in response.
Just since temperatures within the heat exchanger should stay relatively stable when the furnace burners aren't on, your blower fan shouldn't exist needed at all.
And then if your furnace blower is turning on and off when the furnace isn't in a heat cycle, it unremarkably means the fan limit switch is lacking.
Unless you're familiar with the components of your fan limit switch and how it works, nosotros propose letting a professional repair or replace the switch.
Need aid from a MN tech?
If y'all're not sure why your furnace blower is cycling on and off when it shouldn't be, we're here to assistance.
If y'all live in the Minneapolis-St. Paul area, schedule your engagement with MSP today.
We'll transport a tech over immediately to take a look at your organisation and fix the problem in no fourth dimension.
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Source: https://mspplumbingheatingair.com/blog/why-does-my-furnace-blower-turn-on-and-off-constantly