Have 99 9610 with a redekopp mav chopper. Straw chopper alarm comes on when the separator slows down 5% in heavy spots. I think book says that alarm should go off when chopper slows down 15%. Changed sensor on chopper shaft and the magnet is good. Have single drive belt from engine to jack shaft and then double to chopper. Don't think it is the belt slipping because if running empty and move hydro lever forward a little too fast causing the engine to slow down the alarm goes off. Any ideas.