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M Oglesby
M Oglesby, HVAC Technician
Category: HVAC
Satisfied Customers: 2038
Experience:  Universally Certified HVACR Technician
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My heat is blowing out cold air from the vents

Customer Question

My heat is blowing out cold air from the vents, but only the downstairs unit, the upstairs unit is fine. What could be wrong?

Submitted: 6 years ago.
Category: HVAC
Expert:  M Oglesby replied 6 years ago.

Go to the downstairs furnace and remove the panel doors. Observe the ignition sequence. Does the inducer fan motor come on a call ? The inducer Fan is connected to the flue pipes. It is located inside the furnace cabinet and has a rubber hose attached to it.

Customer: replied 6 years ago.

I don't even know where my furnace is. The only thing I see in the garage is the water heater. Where is my furnace?

Expert:  M Oglesby replied 6 years ago.

Where are the vents in your house? Are they in the Ceiling or Floor?

Customer: replied 6 years ago.

Ceiling

Expert:  M Oglesby replied 6 years ago.
Then your furnace is located in the Attic.
Customer: replied 6 years ago.

The upstairs furnace is not lighting up when heat is on vs. the downstairs unit is...

Expert:  M Oglesby replied 6 years ago.

Go to the furnace and look through the sight glass and see if there is a blinking light coming from the control board. If there is, what pattern is the light blinking in? 1 blink pause 2 blink pause 3 blink pause...etc..?

Customer: replied 6 years ago.
3 blink pause
Expert:  M Oglesby replied 6 years ago.

That is an open pressure switch code. You will need to remove the furnace cabinet and locate the inducer Fan motor. The inducer fan motor is inside the furnace cabinet connected to the flue pipes. It has a rubber hose attached to it that connects to a pressure switch. We will need to perform a few tests to find out the problem. First remove the rubber hose from the Inducer Fan Motor and the pressure switch. Blow in it to make sure it is clear. Also make sure there are no breaks or tares in it. Then use a paper clip or nail to clean the Inducer motor connection and make sure it is clear. Re-attach the hose then call . Let me know if this corrects the problem or not.

Customer: replied 6 years ago.

This did not do anything, still blinking 3 times

Expert:  M Oglesby replied 6 years ago.
Remove the two wires attached to the pressure switch. Hold them together metal to metal and see if the furnace attempts ignition.
Customer: replied 6 years ago.

Yes, it sparked

Expert:  M Oglesby replied 6 years ago.
Did the burners ignite?
Customer: replied 6 years ago.

No

Customer: replied 6 years ago.

Where is the pressure switch? It is on the door like a fridge where if you don't press it nothing happens?

Expert:  M Oglesby replied 6 years ago.

The pressure switch is the device that the two wires that you held together were attached to. If it does not close, the igniter will not attempt to ignite. You have a bad pressure switch. You will need to replace it or have a tech. come out and replace it.

Customer: replied 6 years ago.

You said two wires near pressure switch. I'm not sure where the pressure switch is but there are more than two wires where I thought the pressure switch was. There is a switch that you press if you want the furnace to work and I thought that was the pressure switch but that has 3 sets of two wires so that can't be right, other than that I do not see a switch that only has two wires attached.

Expert:  M Oglesby replied 6 years ago.

You told me earlier that the inducer Fan Motor does come on. The rubber hose that attaches to the Inducer Fan Motor connects to the pressure switch. It is a semi round device. If you locate it, remove the two wires that are attached to it and hold them together metal to metal. See if the burners will ignite.

Expert:  M Oglesby replied 6 years ago.

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