Lennox furnace

Switched the furnace on today and it wouldn't heat. The fan for the exhaust pipe comes on, but the burner won't light. The two green indicator lights on the works are blinking green (fast blink) It worked fine six months ago. Gas company wants $85 to come out and look at it. Any suggestions? It's s Lennox Surelight Elite series.
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This is Turtle.
The Gas Company wants $85.00 to come look at it but what does it cost for a person that does this repair service for a living want ? Gas Company hire the least skilled personel to work on these furnaces and the HVAC contractor pay the most for tech's to do this type of work. The Gas company around here did hire HVAC tech for the furnaces at $11.00 a hour and the hvac service companys paid $20.00 a hour for their tech's. The gas company tech just as soon as they really got good at what they did. They went to work for the HVAC service company for you had to know what you was doing to work for them but with the gas company you could be a rookie and get by.
By what you said here it could be atleast 20 different things and maybe a few more added in. You would have to give a more in detail info on this to even get started.
You call the gas company about the fuel supply to your home and the HVAC service companys for to work on them.
TURTLE
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Is there a flame sensor that need to be cleaned, my old furnace used to try and lite, the the draft fan for the flue would come on but the flame on the burner would not lite.
I removed the sensor wiped it off and reinstalled it and no more problems.
Tom

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This is Turtle.
The repair of these furnaces use to be pretty simple until they started using computor relay boards on them. This brought on about 16 sencers, relays, and prover switches added along with the relay board. They have the flame sencer as you spoke of , 8 flame roll out prover switches, and the list goes on. The OP said the vent fan will come on and then not work from there on. This leaves out the flame sencer because if it weas the flame sencer ir would let it light and go out about 15 seconds after lighting. By what he said it probley is the vent fan prover switch , Gas valve pilot lite switch, Timer sequancer in relay board, High temp switch in vent gas chamber, reverse polaritys of electric service, Loss of ground to furnace or to 24 volt transformer, Vent fan not coming up to correct speed, and maybe a funny onme here where it is getting no gas to the furnace. You did not pay gas bill, got the gas valve cut off , or gas valve pressure regulator went out.
Without a great amount of detail it is very hard to fix over the internet because of the person is not looking at it as it starts to run and see the chain of events. The chain of events is a very big part in telling what is the problem. Years ago they were simple and easy to fix. Now days they got high tech and simple went out the window.
TURTLE
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