Has anyone used the Fiero Store 140 amp alternator? Any opinion on quality and so forth?

I may have a failing alternator, and I'm working on installing an aftermarket stereo system with an amp and it requires heavy power and ground cables. The power gets connected directly to the battery.

With a powerful high wattage sound system, you will most likely need an alternator upgrade. The GM CS130 is a logical choice and they are available tp 220 amps. You may need to change the connector on some model years. Many guys here on this forum have done the upgrade and hopefully they will chime in

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" THE BLACK PARALYZER" -87GT 3800SC Series III engine, custom ZZP /Frozen Boost Intercooler setup, 3.4" Pulley, Northstar TB, LS1 MAF, 3" Spintech/Hedman Exhaust, P-log Manifold, Autolite 104's, MSD wires, Custom CAI, 4T65eHD w. custom axles, Champion Radiator, S10 Brake Booster, HP Tuners VCM Suite.
"THE COLUSSUS"
87GT - ALL OUT 3.4L Turbocharged engine, Garrett Hybrid Turbo, MSD ign., modified TH125H
" ON THE LOOSE WITHOUT THE JUICE "

OK, so this is driving me nuts. Electrical issues. Great.

I was driving my Formula, and the engine suddenly lost power and died. Wouldn't restart. Seemed like the classic Ignition Module failure. Fortunately, it was about 3 blocks from my house. I went home for parts and tools, then replaced the ignition module. No change. Swapped out the coil (known good coil), and it fired right up and I drove it home. I just test drove it, and it seems to be running normally.

I am planning to change the alternator to the Fiero Store 140 amp model, since I'm installing an aftermarket stereo amp. I have the alternator, but before I swap it I wanted to do a charging system test to make sure there isn't a problem that might have taken out the coil. I did the tests in the FSM.

Lamp tests
With power on but engine off, lamp should light. Tests good.

With engine running, lamp should turn off. Tests good.

No high/low indications on the gauge needle.

"L" wire test
Disconnected the wiring harness plug at the alternator, then tested voltage from the "L" terminal to ground. Should see voltage, meter says "0.0" volts. Should be a problem, but the car runs and the battery doesn't deplete.

Load test
Run engine, turn stuff on for load and test. No negative indications. I don't have a "carbon pile", so I used a Harbor Freight battery load tester. Gauge on tester indicated ok. I flipped the load switch and the alternator belt started squealing. Turned off the load, squeal stopped. Hmmm. Yes, I get a squeal on startup, but it clears (which often happens on Fieros).

So now I have a mystery. Is the alternator bad? Is there a wiring issue?