My bryant furnace model 100-394u won't light up.the gas is on,the pilot is on but it still won't light. Last year I put a new hunter thermostat and it worked all winter but this year it won't start any advise

Wow,, if you got a year out of a hunter tstat,consider yourself lucky, they are junk

Check to see if you have 24v at the gas valve(when the thermostat is calling for heat). If you don't have 24v, jump from R to W on the low voltage. If no flame or 24v on the gas valve after that make sure you have a 115v to power the furnace and transformer. Make sure you put the gas valve back to on after lighting the pilot. This unit has to be around 30 years old.