400E Illumination Problem

[p0dingt0n]

I have had this car for a year and have tried to get my heater switch buttons to light up, i have checked fuses and replaced bulbs. The dimmer works OK, ashtray and instrument lights OK.
A strange thing happened this week i turned the volume up way too high on my stereo and the lights blinked to the beat of the music, also the window switches and center console switches all did the same. It does have a new stereo in it an Alpine head unit with cassette and radio, i didn't install the stereo it came with the car. Also if i turn the stereo up too high it will cut-out.