Im having a problem with my 86 trans am.The other weekend i gave a guy a jumpstart and i did the big no-no,I put the jumper cables directly to both our batteries.Since then i notice my voltage started to drop more and more till a day or 2 later the battery died.I figured i fried my alternator so i took it back for a new one.The guy at pepboys said my alternator was fine.But i insisted on a new one.I used my other car to give me a jumpstart and the car fired right up but after taking the jumper cables off the battery died and the car died.So now i decided maybe my battery was just beat,so i bought a brand new battery.I put it in and same deal.Id hook up the voltmeter and with the jumper cables on its a lil more than 12 volts,then when i have the car running i pull the jumper cables and i watch the volts drop all the way down fairly fast as if the alternator isnt doing its job.I had this alternator tested too b4 i put it in and its fine and the old one was fine.The volts drop so fast its almost as if my alternators doing the opposite and instead of charging its dis-charging.Any ideas????

 

From working at the parts store it's a common thing for the nice person to fry their alternator while jumping off someone. You put on a new alt. ok but when you put in the new bat. and jumping it off yet again you probably arcked the system and yet again fryed the alt. ADVICE when jumping someone off turn both vehicles off and leave your's off then try to start the other vehicle. Oh and make shure the clocking on the alternator is correct.

 

Don't know what your problem is but it's not how you connected the jumpers, nothing wrong with that except you might blow the battery up if it's outgassing, and that's not very common with modern sealed batterys. You didn't hook the cables to the wrong post by mistake did you? Even if it was just long enough to make a spark it could short out something in the system and cause problems. Sometimes jumping somebody off will fry something even if you do it correctly, but I've jumped off a bunch of people with my car and never had a problem.

 

Yea i did hook the cables up to the right terminals.Im thinking the problem hasto do with whatever the brown alternator wire goes to.I tested the voltage going to the thick red wire and its about 12.12 volts.Then i tested the red and brown wires in the alternator harness.The red was at about 12.11 volts.With the car in accessories,the brown read about 15 volts.I think something in that brown line is messed up.As a test,I cut the brown wire and took only the end going to the alternator and applied 12 volts to it and the alternator began charging perfectly fine.Shouild that brown line be giving the alternator some voltage to turn it on and trigger it to charge?Any ideas???Anyone know the places i can check where that brown wire might run.Does it maybe go to my stereo as well as to the ignition and or fuse box???

 

So maybe ill try running the brown wire to an accessories wire then.The only thing that scares me is that when i give that brown wire juice,the alternator then squeals loud,when i take the voltage away from the brown wire the squealing stops.Im just scared the squealing might be me burning something up when i do that.

 

Brown wire is the "sense" line. Look under the dash at the fuse panel for a fuse labeled "fan/chg" or something similiar. See if it's blown. You can't get 15 volts, there had to have been a mistake when measuring unless it was running with the plug out of the alt. The sense wire is critical in 3 wire systems. Sounds like you found the problem.

 

Well i checked the fuse along with all of my fuses and theyre fine.Is the brown "sense" wire supposed to get 12 volts?I know theres supposed to be a resistor or diode in the line somewhere and im thinking it burned up causing my problem.And does anyone know where in the line the diode or resistor might be.Thanks a lot guys...