If your furnace stops working and you're concerned if it's a minor issue or something major, it's a good idea to find out first if you should call a repairman.  On one hand a service call can get your furnace back in shape, and on the other a simple self-diagnostic can spare your wallet!  If your furnace needs a costly repair, or if it's eating your bank account up with heating costs, it may be time for replacement.  Find free advice here!