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Phil
Phil, Mechanical Engineer
Category: HVAC
Satisfied Customers: 6022
Experience:  Retired HVAC/ Electrical & Boiler contractor. Industrial
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Furnace comes on I have flame blows cool not warm, yes, if I

Customer Question

furnace comes on I have flame blows cool not warm
JA: Did you check the furnace's filters?
Customer: yes
JA: Do you plan on doing the work yourself?
Customer: if I know the problem
JA: Anything else we should know to help you best?
Customer: no
Submitted: 6 months ago.
Category: HVAC
Expert:  Rick replied 6 months ago.

Welcome to Just Answer, my name is ***** ***** I will do my best to help you with your issue. First I’ll need some more info so I have a more complete picture of you situation.

What is the brand and model number of your furnace?

Customer: replied 6 months ago.
nordyne m1m
Expert:  Rick replied 6 months ago.

What are you getting for a flash code on the circuit board LED? How many flashes before it pauses then repeats?

Customer: replied 6 months ago.
nordyne m1m no flash good
Expert:  Rick replied 6 months ago.

I don't understand. There is an LED on the control board/module. Is it flashing?

Customer: replied 6 months ago.
no
Expert:  Rick replied 6 months ago.

Is it on?

Customer: replied 6 months ago.
no yes
Customer: replied 6 months ago.
Expert:  Rick replied 6 months ago.

So the burner fires up the blower comes on but it's blowing cool air?? Do you have AC?

Expert:  Rick replied 6 months ago.

Are you still there?

Customer: replied 6 months ago.
still heare
Expert:  Rick replied 6 months ago.

I need an answer to my last questions. Does the burner fire up, stay on, blower comes on and you get cold air? If so do you have central AC?

Customer: replied 6 months ago.
ok
Expert:  Rick replied 6 months ago.

I'm going to open this up to my colleagues so one of them can help. Please don't respond (even to acknowledge this post)until you get a response from us. If you respond first it will only delay your answer.

Expert:  Phil replied 6 months ago.

Hello, so far it sounds like a pilot light (small burner) might be coming on, but not the very large main burners..... look that aspect over, we can go from there.

Customer: replied 6 months ago.
yellow light not flashing flame ok
Expert:  Phil replied 6 months ago.

Hello, I need a fully detailed description of the flame....

Just so you know, IF the main burners were actually on, and the main blower were on.... the house would warm up, or the furnace would burn up...all that heat has to go somewhere.

So far it sounds like a very small flame, due to a failing gas valve or pilot controls... that is why I need to know about how long the flame is, and what diameter and if it is just in one spot, or across all 4 or 5 main burners.

Customer: replied 6 months ago.
flame is about a foot long and 3inchis wide only one flame
Expert:  Phil replied 6 months ago.

Thanks, ***** ***** like only one of the main burners is operating....that would supply slightly warm air from the vents but not enough to heat the house...that air would be about 5 degrees warmer than the room air.

Can you tell me how many more burners there are? and if not attach a photo showing the entire burner area from about 8 feet away so I can assess the situation.

I need the brand and model number of the furnace as well, its on a tag in the same compartment as the gas valve.

Use the paper clip icon to the right end end of your tool bar or the attach files link to the left of your send button to send pictures.

It will be best to shut the gas off to the furnace until I see what you have exactly.

We can go from there.

Expert:  Phil replied 6 months ago.

Ooops I see you have a nordyne M1M

Expert:  Phil replied 6 months ago.

http://yaunco.com/pdfs/nordyne/Residential/m1install.pdf

Is this what you have?
The MIM model shows as a gas furnace, please confirm.

An oil furnace is a different model number and only has ONE burner with a flame as you describe... it is also possible that someone converted to oil from natural gas... In either case if the flame was adjusted too rich, carbon would have built up in the heat exchanger and greatly limited the amount of heat produced.

Gingerly feel the vent stack and tell me if it is burning hot or just faintly warm.

We can go from there.

Customer: replied 6 months ago.
I m1m vent stack is cool furnace is gas never oil
Customer: replied 6 months ago.
I think it could be sensor
Customer: replied 6 months ago.
are you still there
Expert:  Phil replied 6 months ago.

I am here, I must come and go to do research, type answers and handle several customers at once.

Expert:  Phil replied 6 months ago.

If you have continuous flame, its not a sensor problem... if the flame is only intermittent then indeed it could be a bad high temperature safety cut off limit

Expert:  Phil replied 6 months ago.

I am 75 years old, boiler/ furnace licensed 51 of those years, this would be the very first time I saw a cool vent stack with the burners running...its a virtual impossibility. We might have our terms crossed.

Expert:  Phil replied 6 months ago.

I will be up for another hour or so tonight.. if I miss you tonight I will pick up your response first thing in the morning.

Customer: replied 6 months ago.
ok pick in the morming
Expert:  Phil replied 6 months ago.

If you have that main burner flame, and the are getting good air flow out the 'warm air' vents the house, and that air is not at least 30 degrees F warmer than than the room air.... then... it is most likely that the furnace heat exchanger is fouled with soot (that happens when the burner is set so rich that there is a lot of orange in the flame.)

Tell me about the color of the main burner flame. We can go from there.

Customer: replied 6 months ago.
flame is blue
Expert:  Phil replied 6 months ago.

Thanks, ***** ***** flame, and main blower runnning does not compute with anything wrong with the furnace itself. Perhaps one of the supply or return air ducts has come loose under the house (or in the attic).....inspect for that.

Customer: replied 6 months ago.
have air flow in all vents
Customer: replied 6 months ago.
you still there
Expert:  Phil replied 6 months ago.

Hello again, I was out for a long lunch with clients.

If the burner operates and you have air flow at all the vents, the one and only thing that makes any sense at all is a disconnected return air duct.

I am at my limits on this however, I will opt out and we can see if anyone else has a better idea.

Expert:  airheatman replied 6 months ago.

I am a different expert. First of all look outside and make sure the outdoor ac unit is not running along with the furnace.We will go from here.