2006 lexus gs300 voltage regulator intermitant, whilst driving the battery light comes on ,i give a few more revs and it goes out..its gotta be the alternator

[chucky007]

2006 lexus gs300 voltage regulator intermitant

[Lexus Owners Club]

Could be the drivebelt slipping slightly....any noise when revved or at idle?

Also, have known to have the wrong diameter pulley with replacement alternators and this issue occurs

[CruzinGS]

The 3GS models were some of the first Toyotas to be equipped with a special alternator pulley known as an OAD or "overrunning alternator decoupler" pulley. It allows the alternator to freewheel when the engine decelerates, and has a torque shock absorbing spring to reduce strain and vibration on acceleration. The early models (?) seem to have come with a pulley that does not have a protective cap, so the OAD pulley wears faster. If the pulley is failing, it can underdrive the alternator, and you'll get a reduced alternator output. Another sign of a failing OAD is to rev the motor to ~2000RPM, and shut it off -- a failing OAD will squeak/squeal until the alternator rotor comes to a stop. That all said, it's probably better to replace the alternator (and pulley) as a unit, as you need to remove the alternator to unmount the pulley (Toyota does not include a splined recess or other way to lock the alternator shaft, so you have to hold the pulley with a towel or something and use an impact driver to spin the pulley off). RockAuto has alternators starting at $79+core, and an O.E. Denso-branded reman is $149+core currently.