# Gas furnace not firing



## bulldogsallee (Jan 2, 2012)

I have a gas furnace that will not fire when the thermostat calls for heat, the fan will blow but the gas will not ignite. it is a newer that does not have a pilot light. any suggestions?


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## Koot (Nov 25, 2007)

It's likely that your hot surface ignitor has failed. I suggest always keeping a spare. They're easy to change.


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## bulldogsallee (Jan 2, 2012)

there's no clicking no noise....the fan just starts blowing.....still sound like the igniter?


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## Koot (Nov 25, 2007)

bulldogsallee said:


> there's no clicking no noise....the fan just starts blowing.....still sound like the igniter?


Yes, that's what usually happens...

If you can open the service door and find where the ignitor is located, you might be able to visually see the ignitor (through a ventilation fin in the service door) to see if it is working. If the ignitor is working it will get cherry red very quickly and then white hot when the thermostat calls for heat. If the ignitor does not get hot then solenoid valve that controls the gas flow will not open. If you are unable to visually see the ignitor through a ventilation fin in the service door, you could always just take the service door off and defeat the service door's safety interlock mechanism so you can easily see the ignitor - and see if the ignitor is working.

Betcha $5 you need a new ignitor. Bundle up!


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## bulldogsallee (Jan 2, 2012)

Where in the DFW metroplex can I find that ignitor?


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## Soundy (Feb 17, 2006)

I'd think most appliance shops would carry it... or check with a heating-and-plumbing store. Or, look up the manufacturer of your furnace, then check their website for a list of authorized dealers/repair centers.


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## Koot (Nov 25, 2007)

bulldogsallee said:


> Where in the DFW metroplex can I find that ignitor?


First, get the brand and model of your furnace. Call a HVAC wholesale distributor in the DFW area and ask if they have an ignitor for your particular brand and model furnace. If they don't carry it - they can tell you who does.

What is the brand name of the furnace you have? What is the model?

I'm in Plano. Tell me the brand and model number of your furnace, and where in the DFW you are located, and I'll give you some places to check. In the meantime, here are a few places you can check in the DFW area:

http://www.johnsonsupply.com/default.aspx?menuitemid=910&menugroup=__newHome2

http://www.acsupplytexas.com/

http://www.standardsupplyhvac.com/locations.html


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## bulldogsallee (Jan 2, 2012)

Got the new ignitor installed and still not working.....any thoughts?


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## Koot (Nov 25, 2007)

bulldogsallee said:


> Got the new ignitor installed and still not working.....any thoughts?


It's now time to have a qualified service man familiar with your furnace brand inspect and repair the problem.


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## bulldogsallee (Jan 2, 2012)

Limit switch


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## Koot (Nov 25, 2007)

bulldogsallee said:


> Limit switch


All you said was "limit switch'. What are you saying? What about a limit switch?


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## K7M (Feb 27, 2000)

If you can follow the wiring, there is and ignition board. follow the power lead off the board back to the power source. in series with that wire there should be a limit switch, and a sail switch. The sail switch senses air flow in the combustion blower. If this circuit is not completed the board will not get power to ignite the furnace. Another thing to check (I've had it happen) check to make sure someone did not turn off the gas valve feeding the furnace.


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## juliocolon487 (Jan 22, 2012)

Check your pressure switch, its at the end of a rubber hose that come out from the induced motor, exhaust motor. Usually there are two wires that connect to the pressure switch. Round usually black plastic or metal. Jump both wires. That is the step between the fan and the igniter. If the ignigter is glowing then disregard that step and check the burners assembly to clean the orifice to make sure gas is flowing down the chamber where the igniter is.


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