I have a KCM831 monospace, with a detector edge that says COL, or curtain of light. Center opening doors, the detectors mount at the back of the sill on both sides, and do not move. my question is how in the hell do you replace it, i have a bad one, and it looks like it will need 2 people, and even then it does not look like it will be fun, maybe someone who has installed, can give me some advice. also, does anyone have the part number for this beast of a detector edge? who would design such a thing.