Lennox furnace pilot trouble

Old 11-30-00, 06:52 AM
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I have a natural gas Lennox furnace and the pilot light goes out.It may stay lit for hours, days,or weeks then go out.I have replaced the thermalcouple and adjusted the pilot flame.It is still doing the same thing.I am thinking the gas ignition valve is faulty.Any ideas?????Mick
Old 11-30-00, 07:45 PM
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Many thermocouples get replaced without any of us ever giving a thought to cleaning the connection in the mag head. So remove the new t-couple you installed and with a cotton swab wipe out the connection where the t-couple screws into.

Be sure the pilot flame isn't too large. It should just encompass <surround> the tip of the t-couple head. The t-couple should be glowing a cherry red hot color. If not, the pilot flame may be too large or too small.

Should this furnace be over 15 years old, I would suggest you have the local gas service utility company come and service and check it.

The furnace may have developed a hairline crack in the area of the pilot flame. When the firebox heats up the crack opens and the air from the fan might be blowing the pilot flame out.

Good Luck,
Natural Gas Energy Technician and Consultant.
Personal Quote:
"Drive Safely. The Life You Save, May Be Your Own."
Old 12-01-00, 02:39 PM
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Did you by any chance clean the pilot spud located in the pilot assembly. They have a tendency to build up a powder residue which will cut down on the pilot lite temperature. If your pilot lite seems lazy you can change termocouples from now till spring and it will constantly go out.

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