We have a bryant gas furnace model 394HAD, it is about 10 yearsd & we have had the thermocupler replaced once. The problem we are having, is although the pilot is lit, the fan is on , it is blowing cold air. Just turned on heat on the thermostat by settingit to 70 & then flipping switch to heat. Can you tell us what might be the problem? The ignitors are not lighting up.. Thanks