Big Sky Euro

I'm pretty sure that i need to replace the alternator on my jetta but i would just like some reassurance from some of you guys if possible. There is absolutely no power to the car untill you hook the battery up to jumper cables and then it will start just fine, but then when i drive it not even a block to get the alternator tested, it dies completely again. all points to bad alternator right? my only problem knowing for sure is that i had a lot of work done to the charging system during the summer and i was thinking maybe something wrong there? Any input is appreciated thanks guys

Sounds like you are just giving it power so the motor will start. So, it could be the battery if the starter won't turn over - have you tested the voltage on the battery? Basically, with the car not running, you should have about 12V and with it running you should get about 14V. You can do some basic testing if you have a multimeter:

With the (+) meter lead on the (+) battery post and the (-) meter lead on the (-) battery post:

1. if you don't have 12V with the car off, you have a dead battery - it may just need charged, or it is totally dead and may have a bad cell(s).
2. If the battery has a full charge and you have 12V with the car off, but do not have 14V with it running you probably have a bad alternator.
3. If you have 14V with the car running, the alternator is charging, but the battery is not taking or possibly not holding a charge.

Make sure both your (+) and (-) cables are solid, not broken, and have a solid, non-corroded connection to both the car and the battery. Clean the battery posts (baking soda and water works well to neutralize the acid) so there is a good connection throughout the charging system.

the battery and cables are all fairly new, they were purchased about 6 or 7 months ago this is why im thinking alternator but i will throw a multimeter on it tomorrow and give it a shot, thanks!

okay as it turns out its neither the battery or the alternator, its a control module. There was a recall issued for 01 and 02 jettas that were having an intermittent power drain from the control module and since my car sat for so long, this intermittent drain killed it. The only problem is my vin number doesnt show under recall... anyone else with an 01 or 02 should get theirs checked because even if you have the problem you wont know unless you let your car sit for extended periods of time.