book says :
The Heater Switch (3) is illuminated with LEDs whenever
the headlamps or marker lamps are on. The lamp
brightness is adjustable with the dimmer switch
located in the Instrument Cluster. The heater switch
LEDs cannot be adjusted or repaired. If faulty or damaged,
the entire Heater Switch Assembly must be
replaced as a unit. For complete Heater Switch
removal procedures, refer to the Heater Control
removal in the Heating and Air Conditioning section.
(Refer to 24 - HEATING & AIR CONDITIONING/CONTROLS/
HEATER CONTROL - REMOVAL).
But I would think, if none of them light up, it is a circuit problem, not a led problem.
I've never dug into one of those control modules, so that's all I have to add.
( and I hope you meant 2004, not 64 )