by Freon » Tue Jan 15, 2013 11:42 am
Turn off the power. Remove the thermostat like you did before. Now go to the furnace and find where the thermostat wires connect to the control board. Turn on the power to the furnace and jumper the R and W terminals at the control board and see if you get the furnace to light.
If the furnace runs, you may have a bad wire between the thermostat and the furnace. Check the R and W wires within a few feet of the furnace feeling for a possible break in the copper wire that's hidden by the insulation. Do the same at the thermostat.