1992 Explorer factory A/M F/M casette radio! I did a radio clock search and came up empty! My factory manual says to see the Stereo guide book! But I do not have one! There is a button that says clock! But I have pressed it every way possible and have held it in and pressed about every other button while holding it in! That is while the radio is on! I can't even get the clock button to work while the radio is off!!! How do I set the radio clock???