How can I tell if I need a new alternator or battery?

Question

I have a 2003 VW Passat GLX. It has been sitting for about 3 months because I needed to get the breaks replaced and couldn't afford it at the time. After 3 months, I started the car and drove it to the mechanic shop and had the breaks done. I drove it home.... turned it off..... went inside and returned to the car 5 minutes later. All of the sudden it wouldn't start. I jumped it and took it down to AutoZone. The battery light came on and said to check it. AutoZone guys said the battery was bad and he thought the alternator was bad also. Is there anyway to tell if the alternator is bad at the same time the battery is bad? Is there a chance that its just the battery?

I can't afford to fix the alternator at this time, so there is no reason to replace the battery if it will not help.

Answer 1

If you can jump the car and get it there, most Autozones/Checkers, names depending on where you live, are a great and free asset to this particular question. If you choose to utilize one or the other, find one that brings out the monster testing unit on wheels it checks everything as far as the charging system and battery goes also a few other things. The hand held unit is very limited. Some places will even take the battery out of your vehicle and take it to the tester inside the store, if your not mechanically inclined that is, this will be a fair assessment about the battery health.  Also try and find an employee that knows how to work the unit without having to read the manual or fumble around with even simply turning it on. Not bashing anyone, everyone has to start somewhere. It is just an experience I have learned and it could lead to unnecessary parts purchases.

Answer 2

Auto zone should be able to test the battery and not just guess. They also should have the capability to test the alternator. If not then take somewhere else.

Answer 3

If he has a battery tester, he can tell if the alt is charging. He can also load test the battery to see if it is bad. There are ways to tell which is bad. Good Luck!

Answer 4

on the back side of the alternator  there is an electromagnet.  with the engine running the magnet should be attracting metal touched to it.  if it is not attracting,  alt is not working.

it is back center of alt., opposite of the pulley.

Answer 5

a good auto electric dealer should be able to test both