Furnace Pilot Light Won't Stay Lit - Already Replaced Thermocouple


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Old 10-03-12, 08:56 AM
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Furnace Pilot Light Won't Stay Lit - Already Replaced Thermocouple

After replacing the thermocouple, it worked initially for at least a couple of minutes. A couple of days go by, and as I'm changing the humidifier filter, I notice the pilot light is out once again. This time I can't get it to stay lit. I'm thinking of testing the new thermocouple with a multimeter but can they go really go bad that quick? I even tried keeping the lighter pointed at the thermocouple just to make sure it was getting hit by a flame. What gives?
 

Last edited by anthony42992; 10-03-12 at 10:06 AM.
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Old 10-03-12, 01:14 PM
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The usual reason that pilot lights go out is that the pilot burner and pilot orifice are dirty and need to be disassembled and cleaned.

The pilot burner flame should be a solid blue and have a fairly sharp flame like a small blowtorch.

Traces of yellow or a lazy flame that is easily blown around, or out, like a candle flame indicates that cleaning is needed.


It's relatively rare for thermocouples to actually need replacement, but boxcar loads are replaced needlessly each year.
 
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Old 10-03-12, 01:52 PM
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Well, replacing the thermocouple did allow the pilot to stay lit and for the furnace to work for quite a bit. I did also give everything a brief cleaning but I will go back and be more thorough. At any rate, what gives?
 
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Old 10-03-12, 03:12 PM
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Usually you have to disconnect the pilot tubing at the pilot burner and the orifxce can be removed from the pilot burner and the orifice cleaned with the wire from a wire brush.
 
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Old 10-03-12, 05:23 PM
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If you pull the pilot assembly, be sure to leak test connections with soapy water once it's re-lit.
 
 

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