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Dolores
Heater blowing cold air
Dolores

When I raise the thermostat on very cold evenings, the furnace wil stop blowing heat but cold instead. I've tried to then turn it off at the thermostat but it does not respond so we have to unplug at the furnace and reboot. Any thoughts as to why this happens. Other than this, it runs fine; it's only 6 years old.

dj1
Re: Heater blowing cold air
dj1

If it's blowing cold air, chances are the fire is out. Isn't it amazing, heaters always quit in winter time.

What you need is a physical inspection and diagnosis by a reputable a/c tech. Why? because it could be one or two components from a long list of suspects.

Is there gas supply in good pressure?
Does the gas valve open on demand?
Is the igniter working?
Is the circuit board in good shape?
And so on...

When you find out from a tech please update us.

Jack
Re: Heater blowing cold air
Jack

If the furnace tries to light and fails three times it will blow cold air for 2 minutes. Here is a link to how the ignition cycle goes http://gasfurnacestartupsequence.blogspot.com/

You could have a dirty flame sensor, you can clean it with fine emory cloth or a scotchbrite pad.
The ignitor may have failed in which case it will need to be replace. About $40.
If the flue is fed into a large old chimney the down pressure of the cold air may prevent the inducer fan from maintaning proper draft.

Watch the video and see what is not working on you furnace. Include the model and make of the furnace.

Jack

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