My wife's 2002 VW TDI Jetta Wagon recently had the battery dashboard red battery light come on. My attempt to recharge the battery recognized that a battery failure was the cause. I had previous checked with my VW service people at my VW dealership to assure that any attempts to recharge wouldn't endanger the computer electronics.
I also recognized that replacing this battery would mean a reset of the same VW computer system, because as you already know when you remove the battery on the newer VWs it causes the computer to require a reset which if not done correctly can cause serious problems. Therefore I decided to have my VW dealership do the job. While driving to my VW dealership the following dashboard lights appeared - Airbag, ABS, and the Battery light. When the RPMs reached above 2500 the Airbag and ABS light would go off, but the Battery light wouldn't.
The VW dealership testing found that there was a dead cell in the battery. They also found that the alternator was only producing 50% of the power needed. Therefore we agreed to replace both the battery and alternator.
My question here is could the battery problem caused alternator problem???
This battery was the original batter placing it's age just over 5 years. What made this situation a real mindtwist was that I had identified that this battery should be replaced one day prior to the Battery light appearance.
My thought here is that if such a battery failure could cause a related alternator failure, then periodic battery testing when the battery gets older should be a recognizable desired preventive maintenance issue - right?