if everything else is working pull the heater controls and replace the small bulb in behind the panel. if bulb doesnt work check for power on the wires for the bulb, you may have a broken wire somewhere, but start with the simple things like replacing the bulb.
it took me 2 years to notice that the heater controls didnt light up on my truck. since i bought it the light was out. i replaced it and man what a difference.