Sometimes when putting wood in a furnace to make charcoal, the furnace will not smelt it. Changing the stack of coal/charcoal or wood to use does not change the problem. Oddly enough, other furnaces nearby will still be functional and only certain ones will not smelt. The only solution is to break the furnace and replace it in the same location to get it to work correctly. This is an odd problem.
Linked issues
is duplicated by 1
Comments 4
In response to the duplicate of this issue (MC 7665),in 1.5.1, it is not possible to smelt anything smeltable with wood logs by shift-clicking it into the heat source area. It does work with wood planks fine, but one cannot shift-click logs into the heat source area, for instance to smelt iron ore, if the ore is in the furnance before the logs enter the furnance. This occurs in both singleplayer and multiplayer in a clean 1.5.1 install.
Also, other items which are completely or partially made by wood or a heat source (or that are affected by fire that should be burnable in a furnance) that can't be burned are: bows, beds, fire charges, boats, signs, wooden doors, paintings, bowls, wool, leaves, dead bush (like a sapling), fern (like a sapling), grass (like a sapling), and ladders.
Image Proof: http://imgur.com/a/t6iWc (wooden tools are not shown in furnance, but they do burn)
*The first image of the album is all the items I tried to burn in the furnance.*
The reason I say that beds and other items shown (that aren't completely wood) should burn is because noteblocks and jukeboxes burn, and they contain redstone and diamonds (non-wood items).
I don't know if this was just a one time glitch or if other players have experienced it as well.