Audi Repair: Electrical Question, check battery, electrical question

Question
2000 Audi A-6 Quatro twin Turbo V6:
How difficult is it to replace the alternator.
Battery goes dead in 6 miles so I assume alternator is not charging.
How do I isolate if it is the battery not holding a charge or if the alternator is not charging properly?
Thank you in advance,
Kurt


Answer
Any warning lights on?  Could be battery, alternator or a fuse.  If you have a good battery, and drive the car with no lights on, it should last considerably longer than 6 miles.  Before starting the car, check battery voltage, should be around 12V.  With the engine running and above idle, the voltage should be close to 14V.  If the voltages coorespond, then the alternator is OK and it's the battery.  If the voltage does not go up when the engine is running, the alternator may be bad.  Make sure all the fuses are OK.  Let me know,  Jan