Chevrolet Repair: 1998 Chevy 1500 5.7L Low Voltage, fuse box, circuts

Question
I have replaced the alternator and battery 3 times over three years.  The Voltage meter on dash drops to 9 when the truck is under a load, A/C, lights, blinker when in Drive gear.  It slowly comes back to 14 when in Neutral or Park.  Today again, I replaced the alternator and battery and still have the same symptoms.  I have tested both battery and alternator with a meter and it shows low readings and it is not holding at 13.0 to 14.0.  Hope you can help.

Answer
Hi Jason.... voltage at the battery post on the alt should read when running 14.0 or better without any load. any less than 13.9 and you are not getting a charge....check the connections make sure you don't have any corrosion, also check connections at the power control box.(fuse box) under hood. check wireing to the alt for any opens in the circuts...make sure your alt is grounded, if not sure it's getting a good ground put wire from alt housing to a good ground on the engine or back to the battery. check all chassie grounds from engine to frame of truck....most alt problems are a result of bad grounds... hope this helps