does anyone know if the w210 headlamp switch is a common failure item? i have a problem with my fog lights. they don't work at all by pulling out the headlamp switch.

they will intermittently work, sometimes just the left, sometimes just the right, when i shut the car off and get out.

i checked the foglight bulbs and the wiring, i know the wiring is prone to overheating, but it all looks pristine. i changed both bulbs anyways just to test, but no luck. i tested both the grounds and they are continuous to ground with no significant resistance. i tested the +12v at the bulb and i do not see any voltage.

any thoughts? and yes, i have checked all the fuses already. thanks.

edit:

also, if i were to replace it, i see two different part numbers. 210 545 16 04 and 210 545 09 04 and I'm wondering what is the difference between them? are they different parts for different years? or is one a newer part that supersedes the other?