Hi, I have a hunter I-20 which doesn't seem to adjust the arc. No matter how I adjust the arc clockwise or counter clockwise, it continues to rotate 360. I was going to take it apart to see if a gear is shot or something. I know I can unscrew the head from the housing, and removing the filter, but I am not sure how to do anything else. Can it be taken apart any further? I couldn't find any docs on the Hunter website. Thanks in advance.