Okay my furnace is like 40-50 years old my gas was shut of for a short period this summer and it was recently turned back on the pilot is lit and the blwoer works but the furance won't kick on nor will my cental air unit ( the ac is attached to the heating system, its attached to the duct work of my house) no matter what I do with the thermistate it won't do anything, there is a switch on the side of the furnace that turns the blower on manually, and it works fine, what's wrong with the furnace? Is it the furnace or my thermiste that's messed up? I can switchthe thermistate from auto to on and it does nothing no matter whatthe thermistate is set to I still get nothing anyone have any ideas?

I would start by checking to make sure you have 24 volts in the low voltage control circuit. You can check that with a meter.