This is rather long!
2 years ago, my stock alternator was not able to handle 2 100 watt KC offroad lights (installed correctly) at an idle (800 rpm). Anything above idle was fine. So I replaced the alternator. After a few months, this alternator started squealing under load, i.e. headlights, heat, stereo(no amplifiers) all on at same time. So I replaced this alternator. 2 months later, same symptoms. I replaced this alternator with a "high performance" 140 amp Powermaster alternator. 2 months later same symptoms yet again. So I replaced it again with same powermaster alternator. This alternator was fine for the first few months, but then started to develop similar problems, it could not keep the voltage up at a normal level( <14.6 ) with the headlights, heat, and/or 100 watt driving lights on. (I dont feel this is too much to ask out of an alternator!) The electrical system then progressively got worse, and would randomly, and frequently shut down, thus leaving the vehicle stranded temporarily. As time wore on, the system started to blow fuses. Upon replacing the fuse and starting the engine, the alternator would then squeal for long periods of time while trying to recharge the battery, and would sometimes not even charge the battery, and would in turn cause the engine to die again. Replaced the alternator with a new Duralast 93 amp 3 weeks ago, thinking that the voltage regulator was bad (I thought the fuses were blowing because of power surges). This one worked well for the first week, and then started having the same symptoms (would not keep voltage up to 14.6 at idle, squealing to hold charge) with only the headlights on.
All through out this time, I tried several small upgrades. I ran a 4 ga cable off the positive terminal on the battery to a custom terminal for all accesories(driving lights, trail lights, etc) to get thier power. I ran 14 ga solid core (not braided) copper grounds directly off the negative cable to the threaded hole on the alternator case, to the bolts that mount the heater motor, to the frame, to the fenders, on top of all the existing stock grounds. I have all new, TR ignition, ignition control module, the largest battery I could buy; Exide 850 cold cranking amps.
The engine wires are somewhat hacked up, but all connections are secure and clean. There is one 10 ga wire that goes to nothing from the fuse block in the engine compartment that used to be hooked up to something unknown.
I used to think I just had bad alternators, but now I am realizing the odds of me buying 5 bad alternators in a row is pretty slim, and that the problem must be elsehwere. As far as I know, all accessories are wired correctly; from the battery, to a fuse, to a switch, and then to the accessory with a good, solid ground. There must be something that is causing too much resistence, and drawing all power from the alternator, and killing it.
What are peoples thoughts on this? please dont say new Painless Wiring harness
'83 CJ-7, 258, TR ignition, headers, T5/D300, 3" suspension, 1" body, Moser 1 pce axles, Model 20, 3.54:1