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Originally Posted by criderrc
I have a 1999 Lumina that went dead in the Wal-Mart parking lot. They boosted it and I drove it to their repair bay. They put a new battery in it because they thought that was the problem. All seemed fine for a few days. The battery light went out like it should. Then, several days later, the battery light came back on, so I put another alternator on. The Batt light is still on and according to the volt meter, there is only 12.15 volts measured on the alternator and battery.
Does anyone have any idea what the problem could be?
Thanks in advance.
Rick
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I've had similar problems with my /94 lumina (3.4l v6 dohc).
I am always suspicious when batteries and alternators start misbehaving, but it seems that they are indeed related, because if a "bad" battery constantly requires charging, this strain on the alternator tends to 'blow' the rectifier.
The rectifier is really a 10 cent part (but specially made for low voltage high amperage) and is found INSIDE most GM alternators.
When they replace an alternator, usually whats wrong is just 3 possible things:
(1) worn bearings (not common)
(2) worn brushes (small carbon blocks with copper wire are held by springs against the turning shaft and make an electrical connection to the copper coils. These do wear out, but often are fine.
(3) blown rectifier (this is simply a cluster of diodes, mounted on a heatsink).
(4) Another transistor called a regulator also helps to 'regulate' (stabilize) the voltage in the circuit.
Often a 'rebuild' alternator is just cleaned and the rectifier replaced.
Thus you pay an outrageous fee for someone to essentially replace a $2.00 diode.
Whats worse, in my Lumina, the alternator is hard to get at (you can lift the engine out or jack it up).
Check my other message regarding dying batteries in my Lumina.
In my case, I had your problem (battery/alternator) in which the battery apparently blows out the diode in the alternator (and the alternator fails to charge the battery).
And I also had a shorting problem (battery dies when it rains).
And I also still have a problem with the dash lights not turning off (which drains the battery overnight). Apparently that is caused by a relay (which I haven't yet located).
Hope some of this helps.