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BillyHvac, Journeyman HVAC Tech
Category: HVAC
Satisfied Customers: 22521
Experience:  Endorsed for unlimited heating, cooling, oil burners, boilers, refrigeration, hydronics
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I have a Coleman gas furnace model DGAA070BDTA, in mobile home.

Resolved Question:

I have a Coleman gas furnace model DGAA070BDTA, in mobile home. The air pressure switch needs to be replaced (which is an easy fix)-- it took a digger last winter and I blew into one of the rubber hoses until it lit. My problem now is that the burners ignite but won;t stay lit... is this a bad ignitor, or another part?
Submitted: 7 years ago.
Category: HVAC
Expert:  BillyHvac replied 7 years ago.
would you say the flame only last around a few seconds?
Customer: replied 7 years ago.
Exactly, and then it just goes out.
Expert:  BillyHvac replied 7 years ago.
In the burner area ill be a rod with a white porcelin base. Find this rod and sand it off with emery cloth or sand paper then try it.
Customer: replied 7 years ago.

I did that just now, then waited for 3 failed ignitings, then the "indicator light"(green light) blinks once: "ignition failure". What now? Could it be the sensor rod? or Ignition switch?

Customer: replied 7 years ago.
Hello? Did Billy go offline?
Customer: replied 7 years ago.

The gas is flowing okay... I turned furnace on with gas off, waited until I could see the "element(?)" glow, and then turned gas on and it ignited and ran for close to 3 minutes then shut down.


Expert:  BillyHvac replied 7 years ago.
Wow you have a strange one there. Doent sound like flame sense. Is the stack and vent clear to where you would not be faulting on pressure switch?
Customer: replied 7 years ago.
Sorry, don't know what you're talking about. Just a guy with a broken furnace.
Customer: replied 7 years ago.
I have to blow into the lower tube of pressure switch because it's broken, so that's a temporary fix and it should be working otherwise. I intend on ordering one, and then whatever part you think is causing my current problem with the ignition failure.
Expert:  BillyHvac replied 7 years ago.
Sorry, On your furnace is a draft fan that starts up first. IT pulls air through a small tube that closes a air switch. This air switch is a pressure tube. Take tube off and clear and check ends where tube attaches to make sure they are clear.
Customer: replied 7 years ago.
All clear! Make sure to read what I wrote you just before you replied; about blowing thru tube...
Expert:  BillyHvac replied 7 years ago.

Ok, I see we are on the same page. To test the theory (and this is for test only)

remove the 2 wires from the pressure switch. Start the furnace, and after the draft fan is running connect the 2 wires together. This simulates the air switch holding the contacts closed. Remember though that to start, the wires cannot be touching. Start with them apart and join when draft fan runs.

Customer: replied 7 years ago.

Nothing happens, or I should say, the same problem.

When I am blowing thru end of tube of pressure switch, I can see thru little window when it begins to glow, then when the flames ignite, and then they go out; there's where the problem is. Sorry if I'm getting you messed up.

Expert:  BillyHvac replied 7 years ago.
Ok I got ya now. As long as you continue blowing while the flame is lit and the pressure switch is still closed, and you sanded the sensor, it sounds as though it is the control board. The board decides if the flame stays on or not. As long as the items I mentioned were addressed it would be the board. Only other option is if you are on propane and the pressure is low. Then a low LP pressure switch would do the same thing.
Customer: replied 7 years ago.

Not on propane.

So does that mean a new control board?

Expert:  BillyHvac replied 7 years ago.
Yes, IF the sensor is clean and IF the pressure switch is connected.
Customer: replied 7 years ago.
Dagnabbit! It would have to be expensive! Okay, I'll try sanding the sensor again just in case. Thanks for the help, I really appreciate it!
Expert:  BillyHvac replied 7 years ago.
I really appreciate your patience, I had some connection problems and I am not as good with computers as furnaces. Thank you.
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