# The blower on my Lennox furnace won't shut off



## kgduda (Oct 30, 2010)

We have a Lennox furnace, model # G16Q3-75-5. The blower will not shut off on it's own, even after the heat does. The only way to shut it off is to flip the switch at the furnace. what can we do to fix this?


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## Marty S. (Oct 31, 2009)

Odds are the heat exchanger is cracked which is not something you want to mess around with. Call a quality heating and air company to come check it out.


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## nap (Dec 4, 2007)

has it done this since you turned on the furnace for this season or switched it from AC to heat (if applicable?). I would first check the thermostat to see if there is a setting for the fan of "automatic" and "on". It may be as simple as you flipped the switch unintentionally.


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## kgduda (Oct 30, 2010)

We had a new thermostat installed a few months ago, the blower worked fine with the A/C. We turned the heat on for the first time last night, and the blower would not shut off. The thermostat was on automatic, we double checked everything on the thermostat.


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## Plumber101 (Feb 25, 2009)

Do what NAP said and double check that the thermostat fan selection is not set to on. If it is set on auto then the fan/limit switch is stuck.

Open the front of the furnace and look for a silver looking box about 5" long, 3" wide and 1 1/2" deep. If the cover is still on it you should see the words Honeywell. If the cover is missing then you will see a dial that kind'a looks like a clock but in degrees.

With the fan running lightly tap on the box and see if the fan stops running.


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## nap (Dec 4, 2007)

Plumber101 said:


> With the fan running lightly tap on the box and see if the fan stops running.


but do not progress to the next typical nap step, which is; if a little tap doesn't work, continue to escalate the force until it either works, or you are very confident, that particular device will never work again.:whistling2:


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## kgduda (Oct 30, 2010)

The thermostat is set to automatic.
I have tried tapping on the box and yes it does stop the blower, problem is when the heat comes back on, the same thing happens again.

@Plumber101, just trying to fix a problem, not stupid.


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## kenmac (Feb 26, 2009)

kgduda said:


> \@Plumber101, just trying to fix a problem, not stupid.


 
He didn't say you were stupid.. It may supprise you . But, some have found that the t. stat was switched to fan & not on auto. Had a lady call me last week. Her blower wouldn't turn off. She had the t.stat set to fan on


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## Marty S. (Oct 31, 2009)

The limit is sticking and can be replaced. The G16's are getting old and are well known for cracked heat exchangers. That's why I recommend getting it checked out rather then just replacing parts.


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## Mkarim88 (Nov 7, 2020)

kgduda said:


> The thermostat is set to automatic.
> I have tried tapping on the box and yes it does stop the blower, problem is when the heat comes back on, the same thing happens again.
> 
> @Plumber101, just trying to fix a problem, not stupid.


I have the exact same problem, when i tap on the outside of the furnace it stops and then happen again. How did you fix the problem?


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## user_12345a (Nov 23, 2014)

Mkarim88 said:


> I have the exact same problem, when i tap on the outside of the furnace it stops and then happen again. How did you fix the problem?


this thread is 10 years old - why not start a new one and give us the model number.
if u have a g16 too, finances permitting, forget fixing this problem and start getting quotes for a new furnace - yours is probably cracked being 30+ years old.


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