I know that this has been beat to death probably here somewhere. My 2001 Z28 basically stock (Lid....) . Im getting a voltage (dash gauge drops to 12v from 13.5 or higher) and idle drop (dash tach 500 rpm to 450 approx) as soon as the cooling fans turn on while idling at lights weith max AC on. Pretty sure I updated to a 145 amp alternator just over a year ago. A second or so after the drop the pcm seems to catch it and idle returns as well as voltage. Alternator is only a year or so old... battery less than that. Grounds at engine have been cleaned as well as around strut towers and block to fender (basically all grounds under hood)
Due to me allowing someone else to work on it purely out of being involved in other hotrod builds....I haven't been able to enjoy driving it until lately. After multitudes of re-doing some one elses work on the car and various gremlins I'm now able to enjoy driving it. This and a sight stutter at idle seem to be only real things going on at this point.
Anyone have suggestions or a link to a previous thread?

 

upgrade the charge wire. I found mine to be broken at the alternator connection and only had a few strands hanging on. I fixed the connection and added a 4ga wire. I also added a 4ga ground to the block. Voltage drop when the fans cut on is normal from electric motors starting. You "could" add capacitors at the motors to help if it bothers you that much. I think your idle is supposed to be 550rpm too. Maybe the throttle body or the idle air passage is carboned up.... that would cut down on some idle air. Clean all that. 50rpm translates to more than double the rpm at the alternator pulley btw.

 

Will do thanks