Heater / AC controls lighting 04.5 2500

[JTauraso]

A very strange thing happened to me recently. I removed the HVAC control module from the chunk of plastic trim that it is mounted. There were 2 plugs both different and keyed as usual. When I reassembled the dash I found that the HVAC controls were no longer illuminated. I removed it again to check it for lightbulbs but stopped there. I didn't want to take it apart and chance further problem$. Does anyone know how the lighting works on this component??