I have a blown fuse on my furnace circuit board. The air was working fine in sept. the weather changed and stop using ac. Went all through oct using nothing. Tried to turn on the heat today and nothing. Went to the attic to check the fuse in the circuit board and it was blown. Changed it and it blew again. Went and turned off the heat, removed the fuse for the ac. Put in another fuse and it blew when I turned on the heat. What can I check next? My ac guy had a death in his family and won't get here until next week.