The Clock Backlight is Dim or Does not Turn On.
If the clock backlight is dim, it is possible the backlight control is set to L (Low).
Reference the figure below, #18 and #19 below:
Make sure switch #18 LIGHT is switched to ON.
Make sure switch #19 is set to H (High)
If the backlight is off, make sure the clock is plugged into AC power, and if on a switchable outlet, the switch is turned on.