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Burners light up but only stay on for a few seconds. Next sequence works fine

Burners light up but only stay on for a few seconds. Next sequence works fine

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  #1  
Old 02-03-15, 05:05 PM
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Burners light up but only stay on for a few seconds. Next sequence works fine

and the burners stay on for about 5 minutes. It's a Carrier Weathermaker 8000 furnace. I just replaced the flame sensor and no change.
 
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  #2  
Old 02-03-15, 05:13 PM
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You may need to use a meter to measure the flame sensor circuit. You need to make sure the flame sensor actually sits IN the flame. Make sure on first time fireup that the burner where the flame sensor is.... is actually lighting properly.

You may also need to check the burned mounting screws for good solid contact as well as the mounting screws on the ignition module. The ground forms a circuit with the flame sensor and needs to be good in order for the flame sensor to operate properly.
 
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Old 02-04-15, 04:22 PM
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I repositioned the flame sensor slightly after checking my other furnace. I still don't get why there is no problem when the cycle is done on the second try. Then the burners fire up without hesitation.
 
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Old 02-04-15, 04:29 PM
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When we troubleshoot a problem like yours we will connect a microamp meter in line with the flame sensor. That gives us a measurement and from that we can determine if that is the problem.

You repositioned the flame sensor.... did anything change ?
 
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Old 02-04-15, 05:03 PM
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I will have to wait until tomorrow, as this upstairs furnace is not used during the day.
I will certainly let you know tomorrow and I thank you for your input.

I have also ordered a new ignitor as the current one is 16 years old and has never been replaced.
 
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Old 02-04-15, 05:08 PM
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It's extremely rare to have a bad flame sensor. I think I've replaced 2 in 30+years & both were broken. Clean it well with Scotch Brite or fine steel wool. Don't use sand paper or emory cloth.
Make sure your grounds are all clean & tight. Make sure the sensor rod is well into the flame.
 
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Old 02-05-15, 04:22 AM
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There are no error codes so I find this odd
 
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Old 02-05-15, 08:59 AM
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Most controls will try at least 3 times before they present a fault code. Did you clean the new flame rod before installing? If not, you should. There could be left over oils from manufacturing on the rod or mounting bracket.
 
  #9  
Old 03-07-15, 09:28 AM
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After using Scotch Brite to clean the flame rod, wipe it with a clean paper towel to make sure there's no oil left on it from your hands. Also check the electrical connector on end of rod for any corrosion. Clean the connector with the Scotch Brite too.
 
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