Need new alternator

Any charging system trouble codes? With engine running, take voltage reading at alternator bat terminal. Is it the same as across the battery posts? If the reading at the alternator is higher, then there is a problem with wiring circuit from alternator to battery.
There may be a battery temp sensor, that you need to check?
I don't have a wiring diagram for your charging system, so I won't be much help.
With newer vehicles, The charging system is usually computer controlled.
If problem with wiring circuit, somewhere, replacing the components won't fix it.

What's the voltage at the battery with the car running ? Testing an not guessing is the way to do proper diagnostic's ! Battery light staying on , is there B+ voltage at the alternator connection's ? A new alternator won't make a bit of difference if no power to the alternator . Looking at a wiring diagram an testing the electrical circuit ,doing voltage drop testing , plus checking for DTC'S - diagnostic trouble code's . Some vehicle's charging systems are computer controlled . And looking at a wiring diagram i see your vehicles charging system is computer controlled . If you have done so already , take it to the dealer

Could one WHAT be overcharging the other WHAT???

To understand the problem you must first understand that the car runs off of the BATTERY. The job of the alternator is to replace the power that the car uses back to the battery. The car DOES NOT operate off of the alternator (many people do not get this). The charge light comes on when the charging voltage from the alternator is lower than the voltage that is available at the battery posts (that is why the charge light is ALWAYS on when the ignition switch is on but the engine is not running.

If the CHARGING SYSTEM had been PROPERLY tested, you would have seen this in the tests. If you removed your alternator to have it tested, this does not test the charging system in the car.

This can be caused by a failure or high resistance in ANY PART of the charging system. This includes not only the battery and the alternator, but also all of the connecting cables, wires and the ignition switch.

If the battery and alternator are both good, then the problem is most likely a loose or badly corroded battery cable. However, high resistance in the ignition switch circuit to the alternator can also cause this type of problem. The charging system in your car needs to be PROPERLY tested to pinpoint the location of the fault.

Go to web site WWW.HMASERVICE.COM and register your vehicle by VIN #. You'll then have access to shop manuals, wiring diagrams, technical service bulletins, illustrations, etc.
Provided there is no problem with the vehicle's wiring, find out what the charging current is to the battery. I've seen batteries which TEST good, but when under a CHARGE short out internally.
Example: Tested a battery & charging system on a Hyundai Elantra, the battery tested "Healthy" but indicated there was a CHARGING SYSTEM PROBLEM. I checked the battery voltage while the engine was running and found the battery voltage at 14.3 VDC (which was normal). I then used a Digital DC Clamp meter arount the positive (+) battery cable & found the battery was charging at 70 Amps!.. it was supposidly already fully charged (should have only been taking 4 to 6 amps when fully charged).

Best guess without looking/diagnosing the vehicle myself

Maybe this will help.

this sounds like a bad alternator, that is the job of the alternator besides powering your car after start up, the alternator should keep the battery charged, believe it or not cranking your car is the only job your battery has unless you just switch you ignition to accessory, once you start the car everything runs off the alternator , a quick test for the alternator is this , crank the car and very temporarily unhook the positive battery cable, if the car does'nt die after 2 or 3 seconds the the alternator is putting out a charge

The flashing lights seem to be a common issue when the battery charge is low. From your description the battery may need to removed, charged, and tested possibly replaced. If it does require replacement you may want to have the starting /charging system checked. If there is an Autozone,Advanced Auto,or O'reilly's available in your area they will typically check this system out for you at no charge.

It sounds like the battery has gone dead and will need to be replaced due to a bad Alternator. Once you get the car started, check the voltage on the battery, there should be 13.5 to 14.5 Volts. A fully charges battery should have 12 volts with the engine not running and once the engine is running there should be 13.5 Volts with the head lights on and heater on too. If there is less then 12 volts reading on the battery with the engine running, then replace the Alternator. You can pick up a Alternator at Auto Zone and they can give you the step by step instructions to replacing it with common tools and they can also check the Alternator in your car to before you buy the new one. Good luck and hope this helps and insect the wire harness from the battery to the Alternator, look for any sighs of damaged like corrosion and repair any damages to the wire harness.

The odds are the alternator is the problem again. I've installed brand new alternators in the shop that turned out bad. The battery barely had enough juice the crank the car and get it running. Then, the battery was the only thing keeping the engine running with the spark plug until the battery drain completely dead.

If the alternator was working normally, the alternator would have kept the energy up and keep the spark plugs going without the battery's help.

Basically, the battery's job is to start the engine only and the alternator's job is to keep the battery charged and supply energy for the car's needs.

The battery may not charging fully due to a faulty alternator. Charge the battery overnight at 4 to 8 amp rate, then try the starter. If now better, test the battery voltage with engine running. You should read 13.5 to 14.5 volts at the battery posts. If near 12.6 volts, the alternator is not doing it's job. Take the car to your favorite auto parts supplier and have them test the alternator on the car. They usually do this for free as they hope to sell you a new part. A code scanner can clear the pending fault signal from the computer after the repair. Hope this helps.

Had the same problem. Likely the fusible links. Get a Haynes manual with wiring diagram in the back (should be around $15 or so at an auto parts store). I also had to replace the air intake duct and several components of the thermactor air system. One other thought is that the new alternator is not putting out a charge, you might want to check that if you believe everything else is okay. I once replaced an alternator and the new alternator was defective. --Mark http://www.marksatterfield.com