When mounted on a cart using the Cart Assembler, the Liquid Sensors addon allows the cart to detect whether mining a block will cause water or lava to spill in front of the minecart. By default, the Sensors will be yellow. When the minecart reaches a block to mine, the Sensors will turn green if removing the block will not cause water or lava to spill in the cart's path. If a spill would be caused, they will turn red and not mine the block. This has no effect if there is already water or lava in the minecart's path.