Burner shuts down when blower starts


  #1  
Old 04-30-05, 05:57 PM
jbezdic
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Angry Burner shuts down when blower starts

Hi all,

What could be the cause of this...I have a gas furnace (running on LP) that fires up as normal, but as soon as the blower turns on the burners (not sure of technical terms) cut out. After a few minutes the blower turns off and the burners ignite again until the blower comes on, then they cut out again. The exhaust motor is running all the time. It seems like the blower motor shorts something in the burner mechanism everytime the blower starts up. Any thoughts would be appreciated.
 
  #2  
Old 04-30-05, 09:41 PM
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How old is the system? Make/model?

I am guessing the flame is cutting out from pressure switch... Maybe a leak in the heat exchanger?
 
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Old 05-01-05, 03:14 AM
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As Jay said, there could be a leak in the heat exchanger. Is there any change in flame appearance just prior to the burners shutting down? Do the flames move around when the fan comes on? Another problem could be a high temperature limit switch. This is fairly common on furnaces which blow down into the ducts. Filter clean? All registers open & not blocked?
 
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Old 05-01-05, 01:06 PM
jbezdic
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Burner shuts down when blower starts

Originally Posted by Grady
As Jay said, there could be a leak in the heat exchanger. Is there any change in flame appearance just prior to the burners shutting down? Do the flames move around when the fan comes on? Another problem could be a high temperature limit switch. This is fairly common on furnaces which blow down into the ducts. Filter clean? All registers open & not blocked?
No change in the flame appearance. What actually happens is when I hear the relay for the blower click, I hear a click by the burners and off it goes. So the blower isn't actually running yet when the burners turn off, it just is about to turn on.
 
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Old 05-02-05, 03:27 AM
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This problem just started, or slowly over time??

Remove the blower door, press the safty door switch, and see if anything happens..

still haven't answer of how old the system is, and make/model
 
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Old 05-02-05, 11:08 AM
jbezdic
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Burner shuts down when blower starts

Originally Posted by Jay11J
This problem just started, or slowly over time??

Remove the blower door, press the safty door switch, and see if anything happens..

still haven't answer of how old the system is, and make/model

Sorry - Unfortunately it's a furnace at my cabin so I'm not around it very often. I do know it's not any older than about 5 yrs, It's a Janitrol but know sure of model. All my testing I did with the blower door off and me holding in the saftey switch. To me it sounds like a bad relay on the control board cuz everything functions normally up to the point when the relay to turn the blower motor on clicks, then the burner immediately turns off. I was at the cabin 4 wks ago prior to this and it worked fine. I leave it at 50 when we're not there. I did notice the filter was very, very dirty and replaced it before doing all my playing around (testing). I even climbed on the roof to make sure the exhaust pipe wasn't plugged. I was going to just start replacing parts until it works, but was hoping to not have too many spare parts if you know what I mean. Noticed you're in Rochestor, MN. I'm in Hastings, MN and the cabin's in Luck, WI. Thanks for you input.
 
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Old 05-02-05, 11:45 AM
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If you have & know how to use a voltmeter it can be your best friend when trying to locate a problem like this. We know you are loosing voltage to the burner. Just keep going backwards one component at a time until you find the one which is supposed to have power & doesn't. There should be a wiring diagram on the furnace door.
 
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Old 05-03-05, 07:13 AM
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Hello Hastings :-)

I grew up in Lake City, I do miss the River.

Anyway, Don't spend money on parts that not needed.. Like Grady says, take a meter and see where the power is lost. I am thinking it's something simple.
 
  #9  
Old 05-20-05, 08:12 AM
Ghent96
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Make sure you've tested the temperature cut-off or temperature limit switch "thermostat" (on my furnace this is a small metal disk in a plastic housing, mounted on a coil spring). ie - does it recognize the heat exchanger air as being too hot immediately as the blower kicks on, then react by shutting off the burners. You might have to tweak down the blower on setting, and tweak up the blower off setting and burner off setting. On most of these limit switches, that I've seen, it's impossible to set the burner off setting lower than the blower on setting.

In other words, the little sliders occur in this order:
cold/~50
-
-blower off
-
-
-
-
-blower on
-
-burner off (failsafe)
-
-
-
hot/~200


Now in those ranges defined by these slider switches is another one, technically, called "burner on" that is controlled by your thermostat upstairs in the house/cabin.

IF you've played with that, and no help (and used your voltmeter per the other posts in this dicussion), then it has to be the circuit board box. It's expensive to replace, but (except in your case and my own case), they never usually go out.

Get a home warranty, they pay for themselves after just 1 repair such as this, even despite a ~$50 service call charge to you.
 
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Old 11-14-12, 10:53 PM
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This may be an old thread but my info will be useful to those still looking for an answer. When your blower comes on it's obviously "robbing" power from the system. Get your voltmeter and put it on the mfd setting. Check the terminals across the run start capacitor (two brown wires) ifyou dont receive a reading well then theres your answer. Its a common problem with these units for techs to overlook. Mainly because the unit seems to still have "normal" operation.
 
 

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