I have a nodyne furnace over 10 yrs old the furnace will turn on the pilot light will glow red the flame will ignite than go out after 5 seconds. This process will repeat. The blower will not turn on in the auto or on position when turned to heat. The blower works on the cool or off position. This problem started after my initial problem which was the furnace would turn on, the pilot light would glow red, the flame would ignite than it would shut down for a second, than the blower would start up, the light would glow and the flame would ignite. Than the flame would go out after a few seconds and the blower would blow cold until I took off the cover.

Sounds like you have a dirty flame senser. Remove the flame senser and clean it with an abbrasive cloth (steel wool, sand paper, sand cloth, etc. It will have one wire hooked to it, and usually it will be mounted with one sheetmetal screw.. it will most likely be located at opposite side of burner assembly than glow plug. Hope this helps, please let us know. Your flame senser may look something like the pic I posted, or it will look like this, but be L shaped. It will have one metal rod that sits directly in the flame, and be porcelian where it mounts to burner assembly.

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Originally Posted by mygirlsdad77

sounds like you have a dirty flame senser. Remove the flame senser and clean it with an abbrasive cloth (steel wool, sand paper, sand cloth, etc. It will have one wire hooked to it, and usually it will be mounted with one sheetmetal screw.. it will most likely be located at opposite side of burner assembly than glow plug. Hope this helps, please let us know. Your flame senser may look something like the pic i posted, or it will look like this, but be L shaped. It will have one metal rod that sits directly in the flame, and be porcelian where it mounts to burner assembly.

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You were right my blower is now working however my original problem still exist. The furnice will work when I take the panel off and disable the safety device, but when I put the panel on the flame gets erratic and the furnace turns off. The furnace will work when I hold up the panel to the furnace and leave a inch at the top uncovered, that is where the flames are.

You may have a heat exchanger problem. It is time for you to call for ON SITE professional service before further problems arise.

I agree with HVAC1000. But it sounds like you aren't getting enough combustion air. Do you have two plastic pipes off top of furnace that go outside? Check to make sure intake pipe is not blocked. If your combustion air is drawn from within the home make sure area on furnace where intake is located is not blocked. Can you post a pic of your furnace? Like I said, I agree with above post, just want to make sure we aren't missing something simple, however, with symptoms as you describe, better to be safe than sorry. Good luck and please let us know the outcome. Lee.

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Originally Posted by mygirlsdad77

I agree with HVAC1000. But it sounds like you arent getting enough combustion air. Do you have two plastic pipes off top of furnace that go outside? Check to make sure intake pipe is not blocked. If your combustion air is drawn from within the home make sure area on furnace where intake is located is not blocked. Can you post a pic of your furnace? Like i said,, I agree with above post, just want to make sure we arent missing something simple,,however, with symtoms as you describe, better to be safe than sorry. Good luck and please let us know the outcome. Lee.

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I really appreciate the info from you and hvac1000 my furnace has one exhaust pipe that goes into the chimney and the combustion air comes in from the house. I installed a new blower last year and it works great and I tried hooking it up to the cool and heat same result. The cold air returns are clear and I had the ductwork cleaned last year when I bought the house. Is the heat exchanger the a coil.

If you furnace is a high efficiency unit it will have two heat exchangers. A primary and a secondary condensing exchanger. These are located inside the furnace itself and beyond the scope of a homeowners knowledge unless you what to sign up for a heating class and learn the trade. The reason the flame is erratic is probably because of a failure of one of the heat exchangers. This should be serviced by a professional trained to work on these types of units with the special tools and meters to properly determine the exact problem.

This has nothing to do with clean duct work and stuff like that. It is an internal problem and by you playing around with the safety devices looking for a miracle cure you are probably causing more damage.

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Originally Posted by hvac1000

If you furnace is a high efficiency unit it will have two heat exchangers. A primary and a secondary condensing exchanger. These are located inside the furnace itself and beyond the scope of a homeowners knowledge unless you what to sign up for a heating class and learn the trade. The reason the flame is erratic is probably because of a failure of one of the heat exchangers. This should be serviced by a professional trained to work on these types of units with the special tools and meters to properly determine the exact problem.

This has nothing to do with clean duct work and stuff like that. It is an internal problem and by you playing around with the safety devices looking for a miracle cure you are probably causing more damage.

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Thank you for your help it looks like it's time to take advantage of the 30% tax advantage.

The heat exchanger is the interface between the burners and the air. If it's cracked it will heat up too much. If it's cracked, you risk letting in carbon monoxide into the home.

So, unless you have the tools to do a combustion check leave it alone. Some systems have lifetime heat exchanger warranties, some do not. Don't delay.

You could be looking at getting a new furnace or a significant cost to replace the heat exchanger.