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Discussion Starter #1
Quick question,last couple days furnace doesn't seem like the blower kicks in like it used to. Ya used to hear it ignite and then you would hear the blower come on....now you hear it ignite,sits for.a second,then hear the blower,but then it sounds like you hear it ignite again,and then the blower turn on again.....make sense? Any help or ideas appreciated. Thanks guys.
 

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What is brand and model number? Is it 80% efficent AFUE or more? If so do you mean the Combustion Blower or the Blower for the Ductwork? If it is not the efficient type--The furnace could be going off on limit--Check your filter
 

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If you can post up what some info like the poster above asked that would be good. Does it vent out the side of your home or out the roof top? I'm guessing it's a higher efficiency model with a power vent exhaust. The exhaust blower comes on first in these and it sounds like yours cycles that way. The blower will come on and the furnace control will look at the flue pressure post blower in the exhaust. If the pressure is to high due to a restriction it will not allow the ignitor to fire. I would take the one panel off the furnace and watch the start up cycle. You could have an igniter going end of life. You could have a gas valve that's going end of life or the electronic control module is dying. Are you on natural gas, or propane? I'm guessing not oil.
 

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Discussion Starter #4
It's an older furnace,natural gas,vented through the roof. Just replaced filter about a month ago. Once it fires up it blows heat out great. Just seems to struggle to get going. Can't even find a brand or model number. Sounds like the blower for the duct work but I could be wrong.
 

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Capacitor on the blower motor going bad???? So your saying that the blower takes longer to get up to speed than it used to?
 

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Also check the vaccume hose that runs from the pressure switch to the inducer motor, if your furnace is that old it could be dried out and cracked causing it to leak and cuase the pressure switch to open.
 

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If it is a pressure switch that is bad the gas valve will not energize, therefor you will not get any heat. He has heat the way I read his post.
 

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to help here is the normal sequence of operation for a 80% natural gas furnace built in the last 10-15 or so years


T-stat sees a need for heat by temperature set by user...
T-stat calls for heat
inducer motor starts and pulls negative pressure on heat exchanger as it vents out the flue
pressure switch sees negative pressure and allows igniter to glow or spark
once igniter is sparking or glowing the board then sends power to the gas valve
the gas valve opens and lights off the igniter.
the flame sensor then confirms the gas lit and is burning
for around 20-90 seconds the unit warms the heat exchanger
then the board calls for indoor fan motor to come on and blow
once the fan is moving air, then a number of safety switches keep an eye on temperature of heat exchanger, flue, blower compartment, and flame roll out etc etc...


So by reading that, watch your furnace light off. Go thru the s.o.o. and that will help you to describe your problem and possibly help YOU to diagnose it. Just by what you have described, it sounds as if the flame sensor is dirty and not sensing flame on the first or second try.

Pull it out and clean it with emery cloth or light sand paper. Also, i dont care when you changed the filter last, change it again.


Check back in and let us know. Hopefully this will help you to either fix it or describe the problem better. But from where i am sitting it sounds like you just need to have the unit serviced and maintained regularly. A good service guy will perform a pre season check up for 50-75 dollars and during that service

he will clean the flame sensor
check all the safetys
check the manifold pressure inlet and outlet
clean burners
check for carbon monoxide on older systems
check temperature differentials
check amp draw on motors
clean pressure switch port

and all of those things can mean the difference between a good running efficient home furnace and future problems and pre mature failure.
 

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Big Cheif--Good stuff!!
 

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Discussion Starter #13
to help here is the normal sequence of operation for a 80% natural gas furnace built in the last 10-15 or so years


T-stat sees a need for heat by temperature set by user...
T-stat calls for heat
inducer motor starts and pulls negative pressure on heat exchanger as it vents out the flue
pressure switch sees negative pressure and allows igniter to glow or spark
once igniter is sparking or glowing the board then sends power to the gas valve
the gas valve opens and lights off the igniter.
the flame sensor then confirms the gas lit and is burning
for around 20-90 seconds the unit warms the heat exchanger
then the board calls for indoor fan motor to come on and blow
once the fan is moving air, then a number of safety switches keep an eye on temperature of heat exchanger, flue, blower compartment, and flame roll out etc etc...


So by reading that, watch your furnace light off. Go thru the s.o.o. and that will help you to describe your problem and possibly help YOU to diagnose it. Just by what you have described, it sounds as if the flame sensor is dirty and not sensing flame on the first or second try.

Pull it out and clean it with emery cloth or light sand paper. Also, i dont care when you changed the filter last, change it again.


Check back in and let us know. Hopefully this will help you to either fix it or describe the problem better. But from where i am sitting it sounds like you just need to have the unit serviced and maintained regularly. A good service guy will perform a pre season check up for 50-75 dollars and during that service

he will clean the flame sensor
check all the safetys
check the manifold pressure inlet and outlet
clean burners
check for carbon monoxide on older systems
check temperature differentials
check amp draw on motors
clean pressure switch port

and all of those things can mean the difference between a good running efficient home furnace and future problems and pre mature failure.
Thanks a bunch man,gonna go through some things,pry have someone come out and service it. After I posted it started firing up normal,blower would kick on like it should and away it went. This morning it did it again though. Thanks again.
 

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I have a question for the HVAC guys. We had a Trane Heat pump installed in our home about a year ago. But thats not the problem. We remodeled a part of out house and needed a heat vent moved in the house. We paid him for this. Well we crawled under the house the other day and found that the whole house is covered in mold. We looked for what could have caused it. Well come to find out, he had ripped the metal piping out of the duct work and stuffed it with insulation and wrapped it with Duct tape. Well the insulation had blown out of the hole. My question is should he be held account for this or is this the correct way to close off a duct? Also we can't find the guy now but we have his lic#. It is going to cost around $2000.00 to have the mold removed.
 

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Don't mean to scare you but you may want to get the furnace looked at. If its a older furnace check the heat exchanger if it has not been checked lately. Possibly could have a crack and trying to blow out the pilot when the blower comes on.
 

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I have a question for the HVAC guys. We had a Trane Heat pump installed in our home about a year ago. But thats not the problem. We remodeled a part of out house and needed a heat vent moved in the house. We paid him for this. Well we crawled under the house the other day and found that the whole house is covered in mold. We looked for what could have caused it. Well come to find out, he had ripped the metal piping out of the duct work and stuffed it with insulation and wrapped it with Duct tape. Well the insulation had blown out of the hole. My question is should he be held account for this or is this the correct way to close off a duct? Also we can't find the guy now but we have his lic#. It is going to cost around $2000.00 to have the mold removed.

When it comes to crawl spaces, it's hard to tell what causes mold. In my opinion there is no way to prove the open duct caused the mold, and there is no way to prove that a pest or varmint didn't tear the insulation out. In ur case, I would probably call the contractor, and just let him know what's goin on, don't blame him because there really is no way to tell. He atleast needs to know of the situation and maybe he can help with the cost or atleast permanently repair the duct.

Remember the things that mold needs to live, all of them are found underneath a house. I have seen many guys close off ducts that way and not have any problems, but in my opinion it should have had an insulated metal cap installed. But everyone does it differently and for their own reasons.
 

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if its a goodman or janitrol, take the orange hose off of the induced draft motor housing. take a paper clip and stick it in the barbed fitting to clean out the build up. this happens frequently with these.
 

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Discussion Starter #18
I'll take a pic of it for ya guys. See if it rings any bells.
 

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Discussion Starter #19
Ok so i watched it,it ignites it,then for some reason the flame goes out.....then it re ignites it. Is it not detecting something?
 

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sounds like the flame sensor is dirty. there should be a probe with one wire going to it. take it out and clean it off with a used and worn down little stainless steel wire brush. it should shine when your down cleaning it off.
 
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