EpidemicEvan said:
I noticed that the wires that go to the alternator were kinda bad and the coating of the wires were off (I was seeing some bare wire).
Well, this is never a good thing to find, but it depends on how bad the existing wires are.
If you're talking about the two wires which go into the plug on the top of the alternator, and they are simply losing their sheath, then taping them up will probably suffice. These are the "battery voltage sense" and "diagnostic output" wires.
If you're talking about the main "battery" cable which bolts to a post on the back, then you should follow Garry's advice and just replace it. This cable carries the main power from the alternator to the battery.
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The bench tester at the parts house is probably not lying, but cannot simulate all the "real world" conditions an alternator has to live through. Often failures are intermittent and don't show up with a quick test like that. You can't blame the guys at the counter for this.
Our alternator design is fairly standard and well known. It employs a "3-phase" output and has a bank of diodes which form a full-wave rectifier bridge. Two diodes rectify each phase and all three rectified outputs are combined together for the total power output. If you lose one phase, maximum power output will fall by 1/3rd. Lose two phases and maximum output will fall by 2/3rds.
However, even in this condition, if the load does not exceed the power output of the phases still functioning, correct output voltage will still be maintained.
The diode bank dissipates a large amount of heat (due to their internal voltage drop) and they get real hot. Often these diodes will return to normal operation after cooling down, but they are still faulty diodes. Our internal diagnostic circuit is not your simple "voltage" detector, but rather a somewhat sophisticated phase monitor and is designed to monitor the balance of the three phases. The "battery" lamp is triggered when it detects a power output imbalance between the phases.