Alternator Problems 90 mustang

1990 mustang 5.0 automatic .........Im not sure if i am posting this in the right spot.Anyway I have been through 2 batteries and 2 alternatore so far.I have also taken it to the ford dealership and they cant figure out the problem either.The alternator is not charging the battery.I have checked the connections on the alternator and the ones that run over to the battery.I went to auto zone and had the alternator tested and it is working fine.The car will run fine if i dont run any of the electrical stuff inside the car.If i run the A/C it will run for about 5 minutes and then die.The other problem is the turn signals.The hazards work fine but the turn signals dont.I already replaced the fuse for the turn signals and they still dont work.Any help will be greatly appreciated.I have been messing with it for about a month now.It is a 1990 mustang 5.0 automatic

Ford has a TSB out for that one,everytime you replace the alternator,replace the bigplug,the one with 5 or 6 big wires.That plug was known for burning up the alternators and is not reusable.You can get this plug at any parts store.

Thanks for the advice....I fixed it today but the problem with the turn signals still remain.I went to a salvage yard and got the wireing harness off of another mustang.I replaced the harness from the alternator all the way to the other side where the battery is.That included all of the parking lights and the headlights but now the parking lights wont work.Now the alternator is charging the battery.There was a plug to the left turn signal that i had to splice so i think i did it wrong.I will check it later.Thanks....