help with troubleshooting gas furnace?

hi - first time poster, owned my townhome for a year now and am handy but this has me puzzled:
my gas furnace has not been starting when i've turned up the termostat:
i turn the temp up a few degrees above the current temp, the furnace turns on, and the "whoosh" doesn't kick in, so the furnace (fan?) clicks off a minute or two later.
earlier the "whoosh" did start and the furnance started warming up and moving air, but clicked off about five minutes later.
i've reset the breaker, and thermostat. this problem is on and off, worked fine on sunday, but didn't work saturday and today.
my furnace does not have pilot light, says it "automatically ignites"
i had a cleaning last year, so i'm due for another one and was planning to call my local company, but just curious what to expect, or if it's something simple i could reset
i've also googled "furnace, whoosh", and seen some previous answers about cold air from vent blowing out pilot
thanks very much in advance!! i'm in colorado and it's mild temps right now, but want to solve problem before it gets cold again.
i appreciate it
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It sounds like your 'Flame Sensor' is not working. It sits in the flame of the burner and sends a small electrical current that tells the furnace computer that there is indeed a flame there. If it's defective or covered with crud, it won't send the proper signal and the computer will think the burner didn't ignite and shuts the gas off for safety reasons.
On my Lennox furnace, the part is a no brainer to replace.....two screws hold it in, it costs about $15 for the part. But if you call a repairman, you're looking at over $100, I'll guarantee! My furnace was doing the exact same thing as yours and I got by with just cleaning the oxidation/crud off of it. Since it's an intermittent problem, I'll bet that's it!
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Please post where you got them for that price!!
I'll stock up my truck!!
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On Tue, 01 Mar 2005 11:25:48 GMT, "Dr. Hardcrab"

Lennox doesnt have a piece of scrap paper for $15. Much less a part. But then, Rod IS an expert on furnaces and furnace repair so everyone should listen up when he speaks. :-) Bubba
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