1993 LS400, 150 k miles, no PS fluid or other leaks.
Well at least I think it is the alternator. When electrical load increases (headlights, etc) low buzzing sound occurs. Engine RPM does not change. Easily heard in passenger compartment, sounds like comming from engine. I changed the serpentine belt. Alternator and idler pullys, etc, spin easy without noise. Tension indicator in proper range. Would apprecite any thoughts. Thanks - Herm

 

How loud is the noise and does it have any relationship with the engine speed?

 

at constant engine speed (idle) low buzzing is present when headlights are on and absent when headlights are off. Not very loud but noticable.

 

Still trying to find the cause of the low buzzing noise. New info. It is present with either the headlights or air conditioner on. I was thinking it was the compressor but they why would it occur with the A/C off and headlights on ? 1993 LS 400 150k

 

Do you have an sub amp hooked up to your battery? On my old car, I had a double-battery setup that gave me alternator buzz feedback in my speakers. I have also heard, but can't confirm that if you hear alternator buzz, your alternator may be on its way out.

 

No, nothing extra, all factory. Not speaker noise, it is comming from from engine compartment.

Present if A/C OR headlights are on.