606 groaning under load

[dauber]

My 99 606 has been making a groaning noise when you turn the headlights on at idle, it gets louder when you turn the fogs on or turn the wheel. When you shut the lights off the groaning noise goes away. I have to assume the alternator pulley or bearings are going bad but I wanted to see if someone else has been down this road.

I have had no charging issues and the car runs fine besides this annoying noise.

Motor mounts replace 6 months ago, car has 189k