Alright i have a problem with iron fence elevators. If i put a charged magnetizer on top of a pole, everyone who is trying to climb the pole, can't climb it up and will lose hp. Anyone has an idea what my problem is?
It's suffocation damage. I tested it and it only happens in multi-player. Just a minor oversight from making iron fences smaller than one block (You'll notice you only take the damage when your HEAD enters an iron fence block).
As for them not climbing the pole. I tested it and the magnetizer IS working (minus the suffocation damage...) so either it's not a pole, or you're not wearing metal shoes (I'll assume you checked those :P), or you've exceeded the height requirement (18 is within bounds since 20 is the max), or it's not actually receiving power (the magnetizer itself MUST be above/below and connected to the pole. Also, check to make sure the batbox has power in it and that the output face is facing the right way.)
It's really very annoying that iron fence squares can be entered anyway (they have a slight indentation). It makes it so you can free fall in adjacent columns of air (which wouldn't be possible otherwise), but since magnetizers ARE a full block and MUST be above/below the pole they magnetize express elevators longer than 40 blocks are impossible.