I have a 1990 1680 with a 30 ft. 1010 header. So far this season I have cut wheat, rye, oats, and corn. I started to cut grain sorghum yesterday and my reel speed will not adjust when on automatic. When I change it to manual I can change the reel speed to what ever I want. The same dial is used to change reel speed on both manual and auto. I don't understand why it will adjust when in the manual mode but not in the auto mode. Any help would be appreciated.