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Christopher, VW Technician
Category: VW
Satisfied Customers: 438
Experience:  VW Body Electrical Specialist, Expert Level Technician
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2001 New beetle 5-speed battery dead, alternator virtually ...

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2001 New beetle 5-speed battery dead, alternator virtually dead...mechanic states that alternator can be replaced however, it may not be a bad alternator. Recommends bringing to VW dealership for VW specific diagnostic that would verify if there was a problem in the car''s computer control system that was negatively impacting the alternator''s performance. Is this a valid concern or should I just have the alternator replaced? Thanks!


Was the battery light on while the engine is running?

There are a few things that can affect the alternators performance, The alternator itself obviously, The alternator harness (the cable that runs from the alternator to the fuse panel ontop of the battery, and the alternator pulley.

Assuming the alternator and pulley are the original ones in the car i would have your mechanic do a voltage drop across the alternator harness. If he is not familar with such a technique i can assist you on how to measure this.

You will want to locate the alternator and the large cable running to it (there will also be a connector with two wires going into it) remove the little cap that is covering the nut holding the harness onto the alternator. you will want to place one digital voltmeter lead on this nut. The other lead of the Voltmeter will want to go on the most left cable on the fuse panel ontop of the battery, or the positive terminal on the battery, the reading should not be more than .3V if its more i would suggest replacing the Alternator harness as well as the alternator, and retain the OEM pulley.

Please click accept if your satisfied with your answer, if not please respond and i will clarify any uncertainty you have. Feedback is always appreciated!

Customer: replied 8 years ago.
Reply to Christopher's Post: This is my wife's car so I may be a little short on certain details. Earlier this week, she was driving and was forced to stop in traffic behind an accident. She turned the car off and when she went to start it again, it was dead. She got jumped off on the highway and didn't shut the car off until she got home. It hadn't started since. We have tried a portable jumper but was dead. It was towed to Firestone today where they inspected it and basically the rest was sent in the original question. We do not have the tools nor access to a mechanic like you've suggested above.
The alternator and pulley should be original. I do not know if the mechanics at Firestone would be able to perform this voltage drop test you suggest. Assuming the alternator was compromised, my main question has to do with a diagnostic at the dealership pertaining to the main car computer. This is what Firestone potentially warned me about. They stated they had seen in VWs where parts were replaced yet a larger issue persisted and it was linked to the car's computer. Is this a legitimate concern?

Alright, well not necessarily will the engines computer cause any sort of issue like this.

With your explaination above it sounds like you have a bad battery as well as a faulty alternator.

The only reason for a concern with the engines computers causing larger issue's, would be if the car has a electrical draw. Although, the issue you described it sounds more like a charging system issue, as long as your battery isnt dead in a week you should be ok.

To be certain and put your mind to ease, after the charging system issue is resolved you can take the car to the dealer or any good diagnostic shop and have a parasitic draw test performed to see if any computers are draining the battery.

Goodluck with the repairs, and make sure firestone uses the OEM pulley with the alternator they install.

Please click accept if this has helped you. Feedback is always welcomed!

Customer: replied 8 years ago.
Wonderful! Will look for battery issues after replacing alternator. For this "parisitic draw" test, is this something the dealership would normally run or is this a special request? And I think the last question I'd have would be what should this test cost ( in NC)?
My Firestone has been really good for us for a while. They did mention they would be getting an OEM alternator so I'm hoping that includes the pulley arm as well but I will make note when I see them tomorrow. Thank you for all your help and I will click Accept after your next response.

When and If you go in to the dealer after the alternator replacement, Just tell them that you have just replaced the alternator and battery, and would like any faults cleared, and a parasitic amperage draw test (the tecnicians will know what you are refering to, the service advisor might not) performed, ask them for a printout of the readings of the draw test, just for proof they have actually performed the test.

You most likely would be looking at about 1hr of labor for this, and depending on the dealer you take your car to thier labor rate should be in the ballpark of $110.

Goodluck with the repair and if you have anymore concerns feel free to ask!

Feedback is appreciated!

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