I own a 95 volkswagen jetta. Lately it hasn't started correctly. I changed the starter and ignition switch. The starter now engages again but the battery after sitting acouple of days must have went dead. So I jump start it down the hill in front of my house. I let it run awhile in the driveway to recharge the battery so I could test the starter again, when after 10 minutes the power started to fade then the car died. I called a friend to come over and jump start it and it didn,t work. The starter engaged but did not turn over the motor. Finally I rolled it down the hill again the next day and again it ran for 10 minutes and then slowly lost juice. What could it be alernator, battery, or voltage regulator, what?

 

I would think the alternator. Most car parts shops will test an alternator for free, so do tha first.

 

I would tend to agree.

Do an output test with a digital meter and see if you have 14.2 volts with no load engine running, and 13.5 or more at the battery with a full load of accessories at idle.

If not, bad alternator.

 

If you have a separate battery charger, give it a good charge to start with, in case the battery is just discharged; you'll want to make your voltage measurements with a good battery. Sounds like you have a combination of a discharged battery and a faulty charging system at this point.

You might want to check your ground connection to the battery; it can cause all sorts of odd symptoms, like not being able to start even with jumper cables on it. (Using decent cables? Cheap cables may not supply enough current, especially with the extra load of a dead battery)