The following lights do not illuminate when I turn on the headlights:
Radio button lights (only the LED display panel illuminates and it dims when I turn on the headlights)
A/C Switch (only the green light illuminates when it is on and it dims when I turn on the headlights)
Defroster Switch - the normal 'off' does not illuminate with the headlights and the 'on' never illuminates

The passenger visor mirror light does not turn on - the bulb is intact and should work

Any chance these illumination issues are related to a single circuit / fuse with the headlights? The radio buttons, A/C switch and Defroster should all illuminate when I turn on the headlights but they do not.

Prior owner installed a Kenwood 10-CD changer mounted behind the driver seat. It has it's own control unit wired behind into the radio harness. It's an odd unit - plays CD's but they broadcast through the radio as channel 88.3FM. The CD's barely register on the left side of the speaker system even though the radio plays perfectly - might just remove the Kenwood system at this point.