MFR Auto-spawner not spawning wither Skelletons

[AnTerZz]

Hey, My auto spawner isn't spawning any wither skelletons. I am playing on the modsauce pack and believe everything is setup correctly as it was spawning other mobs. The work goes up and the idle up and down but no spawns... Please help

 

[Yusunoha]

I'm guessing because you have the spawner right below the ceiling that the mobs don't have enough room to spawn.
try lowering the spawner a few blocks and try again

 

[epidemia78]

Two minimaps, eh? Maybe things have changed, could be you need to spawn them in the nether?

 

[rhn]

I'm guessing because you have the spawner right below the ceiling that the mobs don't have enough room to spawn.
try lowering the spawner a few blocks and try again

Indeed. The spawner spawns in the vertical area of -1 to +1(this is the block the mobs feet spawn in). Wither skeletons require 3 blocks tall to spawn and you only have 2 blocks tall from the lower limit.

I suggest raising the roof up so there is at least 3 free blocks above the spawner to free up the entire potential spawn area. Else you get slowed down spawn rate due to failed spawns(which is the behavior you are seeing now).