My furnace is blinking 4 times indicating that the furnace has an open limit switch. I changed the switch and it is still blinking 4 times indicating the same thing. What else could be wrong or what can I do to fix this problem? ITS COLD!!

In the line going to the limit switch was there a little fuse, a small thing in the wire that looked like a small firecracker, it will be close to the limit?? That is a roll out fuse but works in line with the limit switch. And I am sure it would give the same 4 blinks. To check this you can use a short piece of wire to jumper around the fuse. If that is the problem DO NOT LEAVE THE WIRE ON AS A JUMPER TO MAKE THE FURNACE RUN. That is a safety fuse and there is something wrong or it would not have blown, it could have been a down draft or something similar but do not take the change.