Gas furnace 1 of 3 burners fires, then shuts off


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Old 02-05-10, 07:47 PM
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Gas furnace 1 of 3 burners fires, then shuts off

I have a RUUD gas furnace about 10 years old. It is located in the attic. It has 3 burner chambers, with an electronic ignition on the rightmost burner.

When it attempts to start, this one burner fires for about 5 seconds, then shuts off. The other 2 burners do not light at all before the unit shuts off. I believe the flame sensor is on the leftmost burner, so it would make sense that the unit is shutting down because no flame is reaching this sensor.

So the question is, what would cause only the 1 burner to fire?

One thing I did notice is that there is a small amount of water down in the bottom of the blower cabinet. We have had rain for the last 2 days, so is it possible that it's just condensation from the furnace running in a cool, humid attic?

I'm in Georgia and the temperature has been around 40F lately.
 
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Old 02-05-10, 10:29 PM
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The usual reason burners don't light is that they are rusty or dirty and need to be taken out and cleaned.

But no doubt water could drown them were it to get to them, which is unlikely. Check for water leaks or drips though since you think it's a possibility.



40 degrees, eh? Frigid!



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Old 02-06-10, 06:16 AM
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SP, thanks for the response.

Yeah, 40 is not real cold, but enough to want some heat.

Shortly after posting last night, the furnace "magically" started working again. This forum really works!!!!

I suspect you are correct that the burners probably could use a good cleaning, as well as the flame sensor. I hope the water has not damaged the circuit board. I'm not sure where that water is coming from, so that's now my real concern. Could be the flue vent stack leaking above the roof somewhere, and water slowly running down into the unit?

Thanks again!!!
 
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Old 02-06-10, 08:45 AM
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Water

I'd suggest checking the chimney cap, presuming the vent to be metal.
 
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Old 02-06-10, 10:25 AM
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Grady, yep, it's metal all the way.

It's not raining today, and everything is dry, so I suspect I've got a small leak in the vent cap, and the water is draining down into the unit. There's not that much, but I guess it will only get worse.

Thanks!!!
 
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Old 02-06-10, 10:55 AM
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Worse

It will indeed only get worse. If the cap is damaged, replacing it is usually not difficult.
 
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Old 02-06-10, 11:14 AM
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Yeah, replacing it is probably not that difficult. Getting up on the 8/12 roof....that's the tricky bit.
 
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Old 02-06-10, 11:20 AM
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8/12 Roof

Better you than me. I don't have nor am I eager to get wings.
 
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Old 02-06-10, 11:23 AM
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I know that this is a DIY forum but sometimes the most important tool a DIYer can have is the checkbook. I don't "do" roofs anymore for several reasons. Call a chimney company and have them replace the cap.
 
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Old 02-06-10, 11:41 AM
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I won't be getting up there either. I know my limits, and that's one of them.
 
 

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