Hi, we purchased a used yankee freestanding unit. I believe it is a 2003 based on the serial number starting with 2103. When burning on low, the firepot builds up with pellets and at the bottom of the firepot, the pellets become like one big chunk. I looked in the manual online and it talks about a restrictor arm. My unit does not have an arm on it. After searching high and low, I found a small knob on the bottom, left of the rear of the unit and am wondering if this could be the restrictor adjustment. If so, how do I adjust it to fix the problem. When I burn on med or high, it burns great but on low, it is a mess. Can anyone help me?? Thanks, Diane