98 ls1 shorted out 4 alternators in 20 miles

[98Z28]

I really need help with this one-- I have a 98 Z28 with 118,000 miles I have owned since almost new-- a year ago the alternator went out put 5k on it then in may the alternator went out again so I took it back in to Chevy dealer and replaced it-- didn't make it home so dealer kept for 6 weeks and replaced again and said not sure why it went out -- 10 miles later went out again so I took it to the Pontiac dealer where I work (last 8 years) actually and our mechanics replaced with another G.M. alternator under warranty and after 15 min of driving started loosing voltage-- parked it--
symptoms after driving for a few miles voltage drops 2 volts with and any load what so ever and gas gauge will read opposite direction -- then if you accelerate very hard at all the dash lights up and register s only battery voltage and a/c goes warm and lights dim--- alternators were checked as bad when pulled -- 2 dealers and a private mechanic and they all say all looks fine but they know there is a problem.-- also when I start the car the volt gauge slowly moves up to about 13.7 when cold again-- this is before complete failure of course --- car is parked at dealer with everyone scratching our heads-- G.M. Tech line won't help since it is older than a 2000 model. no mods other than fast toys ram air and larger Maf flow no maf mod though and a program from a 3.23 car same year when I took the 2.73 out but all this was done 9 years ago new transmission 5 years ago and a/c replaced 3 years ago and starter. this has been a fantastic daily driver till now-- I have to get this car up and running again anyone have any ideas-- I also replaced my optima battery with a new optima battery after this happened and the alt connection has been replaced . the only electrical only shop in town just closed their doors last month.

[JoshieDoom]

First off I would cut all the tape/wrap on the wiring and look for shorts/broken ground straps etc. I went through this last week with a 87 caprice and it turned out two be the starter wire insulation was grounding out, we put 2 alternators, one starter, a brand new distributor and a new EGR valve before stuff stopped breaking.

Start looking for obviously defective wires. Make sure its not something little like a incorrectly placed wire, positive on negative and so on and so fourth.

[sunsetorangess]

I would agree with above, somewhere you have a serious short. Personaly i would start with the most obivious places first, Ie, fuse box, main hot wire, All grounds to ensure there tight and clean. Main positive on starter. etc etc. Recently we found a short by hooking a multimeter to the battery and reading the volts, then we went around tugging on the harness and waiting for the multi-meter to fluctuate when it did, then we dug into that wiring harness.
Just an idear.
Is there anything you do that brings on the low voltage? Like turn on the AC or move the seat or is it just random?
J