ice maker trouble

[mike3278]

not really sure of the age but dosnt look to old. my icemaker makes ice fine but ice builds up on the arm that tells it when the bin is full and it gets stuck in the off position and stops making ice so every night i have to break off the ice buildup. its not a metal wire that goes up and down its a flat piece of plastic that moves back and forward under the ice maker. i do not know why its doing this and how long. it came with the house i bought a month ago. thanks for any help