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freon, Licensed A/C Contractor
Category: HVAC
Satisfied Customers: 215
Experience:  22 years Licensed Contractor State of Texas
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Burning smell coming from furnace vents. What could it be?

Resolved Question:

Burning smell coming from vents. Just changed filter last month. What is it?

Submitted: 6 years ago.
Category: HVAC
Expert:  freon replied 6 years ago.


I would like to help you. Are you in the heating mode or cooling?

Customer: replied 6 years ago.
I was in heating mode but, turned the heater off
Expert:  freon replied 6 years ago.


Normally this burning smell could be: electric heat strips or gas furnace start up if for the first time in a while. Next if you have already been running the unit for a while, it may be the blower motor over heating. Do you have gas or electric heating?

Customer: replied 6 years ago.

It is electric heating

Expert:  freon replied 6 years ago.
Has the heating been off for a while?
Customer: replied 6 years ago.

Only for about a half an hour... Would it take longer for the smell to go away?

Expert:  freon replied 6 years ago.

Well at this point I am not sure if the smell was from the heat strips or if it is from the motor overheating. Now is the fan running still or has it turned off? You may also check this by turning on your fan at the thermostat. Switch it from auto to on position.

Customer: replied 6 years ago.

Would the fan make the smell come out?

Expert:  freon replied 6 years ago.

Yes. But we need to check and make sure the fan is working.... It may have burned up. How old is this heater?

Customer: replied 6 years ago.

Let me go run the fan and see.... About 3 years old, not too old...

Expert:  freon replied 6 years ago.

Ok great,

I hope you are not using pleated filters! They really make your system work hard and usually cost you a lot of extra money in utility costs!!!

Customer: replied 6 years ago.

I just turned the fan on and it seems to still smell through the vents.... What else do you use for filters?

Expert:  freon replied 6 years ago.

Oh you have been using the pleated kind! Here is why I say this... Most people have return air systems that are marginal at best. If you take and put this highly resistive pleated filter in place of the poly (cheep) type you are hurting your system. Some have even ruined the blower motor. Now I am not positive that this is what has occurred at your home but something is definitely wrong.

Do you feel air coming out of the vents?If you see smoke then turn unit off. And call for service. If you can you should also turn off the breaker that services this electric furnace. Do you see smoke?

Customer: replied 6 years ago.

No smoke, but I think the filter was brown in an area that may have been burnt. What filter should we buy?

Expert:  freon replied 6 years ago.

Well honestly I don't see how the filter could be burning. Do you have an electronic air cleaner attached to your Electric furnace?

The cheep filter is called a poly filter or fibre glass filter... They usually run about two dollars at the builders supply store.

Customer: replied 6 years ago.
Ok we will have to get the other filter. I don't know about the electronic air cleaner...
Expert:  freon replied 6 years ago.

Ok let me be clear... Did you buy an electronic air cleaner and have it installed at your home?

This is part of your a/c system and can make the burning smell if you have one of these.

Thank you. Am I asking too many questions? Are you still wanting to locate the burning smell?

Customer: replied 6 years ago.

No we didn't buy an electric air cleaner... Should we still replace the filter and see if that is the problem?

Expert:  freon replied 6 years ago.

Yes. Your motor may have sustained damage... I don't know for sure. However you have been smelling the burning smell and I think it is important for us to figure what is causing it.

Replacing the filter is a long range solution. The short term solution is to remove the pleated filter and run the system for a few hours and see if this helps clear the burning smell.

Customer: replied 6 years ago.

So remove the pleated filter and replace it with the other one and see if that solves the problem??

Expert:  freon replied 6 years ago.


Try this and see if the burning smell goes away. I want to thank you for contacting Just Answers! We appreciate you. If you have any other questions I would be happy to answer them!

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