trying to animate lit furnace texture not working.

i was trying to make my lit-furnace texture animated (and i do know how to animate textures its not my first one) but when i put on that texture pack the front of the furnace becomes "x-rayed" and dos'nt work.
i am in snapshot 13w04a but i am pretty sure this apllies to the earlier snapshots.
i have uploaded the texture i made and the result in minecraft.
( sorry, english is not my first language :\ )