Two problems related to alternator/generator/regulator have been reported for the 2005 Volkswagen GTI. The most recently reported issues are listed below.
My cars electronics would shut off while driving, a few times the car completely stalled while I was driving. The alternator the Volkswagen puts on the automatic Gtis are too small to power everything in the car. They put a 90amp on the car, when it needs something bigger, auto part stores sell a 120 amp. I brought my car to the vw dealership I bought it from, and the guy that sold me the car told me "there is no one here that cares about your problem" so I went home and called vw national office, they took all my information and said they would look into it. During the time they were looking into the problem my battery wouldn't stayed charged, so I bought the 120 amp alternator and a new battery and just replaced them myself. I agree with the other person that complained about this, only happens when it gets really hott outside and you have to run your ac at a higher speed.
I bought a new Volkswagen Gti in '02. Every six days when the temperature went over 85 degrees, the car died and left me stranded. This also happened in moving traffic, and I lost throttle, steering, transmission, and braking ability. Vw replaced the car two months later. The same problems occurred. Every electrical system in the car then began to fail. After two months of research and analysis, since I am a retired federal engineer, I noticed that the factory was putting 90 amp alternators in the automatic transmission cars, and when it got hot, and the cooling fans came on, the alternator could not supply enough power to the battery, which discharged over a 5 or 6 day interval, then stranded people. I reported this to Volkswagen of America. They thanked me for solving a problem their engineers had been unable to fix. I was horrified, when I got a 2005 Gti, to again find myself stranded on the road, helpless, when it got hot. Sure enough, there was a 90 amp alternator in that car, not the required 120 amp. This was 3 years after they acknowledged they had a problem. I was then told that this was not a factory error, but a deliberate decision by vw to save money by using the cheaper alternator. They have stranded totally disabled people like myself, and families, for the past 3 years, to save a few dollars. I was told by vw that when the owner gets stranded, the correct alternator is then put in the vehicle. By then, the electronics have been fried, as has happened with my new car. I ask the government to step in, and order vw to recall all 2002-2005 vw Gtis with automatic transmissions, and to replace my vehicle, which has failed 4 times so far, with a vehicle with the proper alternator in it.