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Old 10-03-2009, 12:20 AM   #1
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Gas is flowing but no spark or fire ... or heat


I have a Plus 90, 398AAW. The furnace was working up until yesterday and then stopped producing heat. The inducer motor comes on and stays on. The blower motor does not come on unless I put the fan setting to ON. While on Auto, the blower doesn't come on. I don't see any pilot light or any clicking sounds. When I go outside and smell the air coming out of inducer air output (not sure what the right name is for that) there is the smell of gas in the air.

So, to me it seems like there is a problem with the electronic ignition, but I would love some feedback if anyone has some advice. I could also use some help identifying and locating what exactly needs to be cleaned, checked, or replaced.

Below is a picture of what is going into my heat exchanger:



1) I'm not sure what this thing is
2) I'm guessing that the red wire is the actual electronic ignitor, what's interesting is that it goes right up into the heat exchanger, there is not way for me to get to it without removing the cover for the heat exchanger and getting inside of it. Below is a closeup of this. Seems kind of scary to open something like that up but I'll do it if that's what it's going to take.
3) This thing is labeled as the "Spark Ignitor", my guess is this is a capacitor that stores power to actual send to the ignitor when it triggers.



I'm not really sure if I should be replacing whats at the end of the red wire going into the heat exchanger or if I should be replacing the black box labeled Electronic Ignitor, or both. I would love any help anyone can provide, it's getting cold in here.
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Old 10-03-2009, 01:02 AM   #2
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Gas is flowing but no spark or fire ... or heat


Do you know how to use a volt meter and read a schematic? If not, the only thing I would recommend is to take off the front cover of the "combustion chamber. Do you hear a spark? Does the system fire up? If it does fire, re-set the cover to see if the problem re-occurs. If so, the problem is likely due to some obstruction with the air-in-take. Good luck
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Old 10-03-2009, 01:33 AM   #3
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Gas is flowing but no spark or fire ... or heat


Thanks Flash,
You got me brave enough to take the cover off the Combustion Chamber. I tried turning it on again, and again, only the inducer motor turns on, no spark (seen or heard) and no flame.

I do have a meter.

Below is what the inside of my combustion chamber looks like.



Let me know if you or anyone else has any more advice.
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Old 10-03-2009, 05:38 AM   #4
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Gas is flowing but no spark or fire ... or heat


if you have a inducer draft motor coming on that is the first item to run then it needs to proof that round switch with the 2 plastic tubes and 2 wires going to it...then the spark...then the main burner.restart the call for heat ID comes on tap the round pressure switch with the end of a screwdriver or quick jump the 2 wires to see if you get ignition for the pilot!if you here the sparking on the ignitor the pressure switch tubes might be blocked(bug) or the switch is stuck open..lets here the results looks like this http://bestbuyheatingandaircondition...&Category_Code=
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Last edited by biggles; 10-03-2009 at 05:41 AM.
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Old 10-03-2009, 08:03 AM   #5
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Gas is flowing but no spark or fire ... or heat


Thank-You Biggles

So I wasn't quite sure how to short the pressure switch. Here is what I did try while the inducer motor was running (and I replaced the Combustion Chamber front cover):

1) I removed the tube going to the Collector Box and when I suck on it manually, I heard the switch click but nothing happened with the ignitor or burner. I also stuck a small screwdriver into the Collector Box to make sure nothing was blocking it. (See Arrow #1 below)
2) I removed the tube that leads to the Burner Enclosure and was able to blow and suck on that freely so it is clear. (See Arrow #2 below)
3) Tapping on it with a screw driver

Below is picture of what I'm working with:


Thanks
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Old 10-03-2009, 09:47 AM   #6
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Gas is flowing but no spark or fire ... or heat


try to blow lightly into the collection box tube going into the silver round pressure switch should get a relay click and a spark to light the pilot..the 2 wires ORANGE/WHITE from the pressure switch look like they OK that white relay and that calls in the cycle to heat.if you put together the orange/white wire after pulling them off the pressure switch that is the same action as if the pressure switch closed when the ID comes on.the pilot spark and burner aren't coming on because ther is no proof closure on that relay down by the pressure switch.lets hear back.....
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Old 10-03-2009, 10:18 AM   #7
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Gas is flowing but no spark or fire ... or heat


So it seems like I should blow into the Burner Enclosure Tube and suck on the Collection Box tube right? Does the switch need to experience pressure through both tubes in order to close?

Regardless, I decided to close the switch by jumpering it like you described. There were three wires going into the pressure switch with these lables, I don't know what they stand for,
Orange - C
Yellow - NC
Brown - NO

I jumpered Orange and Yellow.

Still no impact, Inducer motor runs but no clicking of the ignition or burner firing.

Let me know what you think I should try next!

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Old 10-03-2009, 04:05 PM   #8
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Gas is flowing but no spark or fire ... or heat


thats it with the jumps and the blowing into tubes....... you need to read the 24Vs down and thru the saffties tosee what is stopping the ignition to spark the pilot.
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