Having Furnace Problems?
Furnace issues are much like electrical in that I have to limit the advice I can give. In some ways they are not that difficult, but the consequences of an error are potentially fatal. In addition, since I have no way of knowing what changes/modifications may have been made to the system, mistakes are likely.
The articles linked to below go into significant detail about furnace trouble shooting and repair. In particular note that if you have one of the really old furnaces, they can not and should not be repaired. No matter what your financial situation you must be aware they have the potential to kill you!.