I have an old Lenox G12 natural gas furnace that is not producing any heat. I've turned off the pilot and relit it again with a nice flame. When the fan comes on the flame diminishes somewhat but stays on. However the burner tubes are not lighting up and there is no heat. P.S. There was a slight gas odor when we got home from work.
How much money is your families lives worth? 100 bucks? Get it serviced now, it sounds like you have a cracked heat exchanger. Any change in flame when fan kicks in is a very good indication that the heat exchanger may be comprimised. Do not hesitate, call someone, Carbon Monoxide can kill you and your family!
Better have that checked out by a professional.
I think that your thermo coupler is shot. It will not let the gas come on without the signal that the pilot is burning hot. It's the device that makes it safe. I think if you ground that wire you could check to see if that is the problem. Don't run it without that hooked up however because it would be unsafe.
It could be a bad or incorrectly set thermostat or the furnace main valve might be off (in the pilot position rather than On) or faulty. By the way, if this is a forced air furnace it would be unusual for the fan to come on at all until the burner has heated the firebox to the proper temperature. Bert
THE FURNACE NEEDS CLEANING.YOU HAVE DIRT,RUST FLAKES THAT ARE PROHIBITING THE TUBES TO KICK IN
