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Discussion Starter · #1 ·
Hello,

I recently changed out the alternator on a 2007 2.5 Beetle. Alternator spins but won't charge the battery, I out a voltmeter on the battery and watch the battery slowly die. Anyone have any ideas as to what the issue might be? It looks like everything is plugged in from what I can tell.
 

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Here is a excellent overview of common issues with the mark IV/New Beetle charging system problems; and solid diagnostic, testing procedures, to find the problem.


What brand new alternator did you buy and install? OEM Bosch is recommended.
 

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Discussion Starter · #4 ·
I'm not sure which alternator I bought as it was several months ago. I took the manifold off to see if I connected everything properly. I see I have 2 bolts with one being connected. I've searched everywhere trying to determine if the connection is correct. Can anyone comment on the attached photos to say if I've connected it properly?
 

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Discussion Starter · #7 ·
I looked at both links and it's connected to the same bolt. Just out of curiosity I removed the other bolt and tried to see I could put it on and I am unable to since the bolt moves back and forth just enough to prevent me from threading the nut. One thing I just now noticed is there is a burn mark on the plastic from where the cable connects. Anyone have any thoughts?
 

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Autozone will bench test your alternator for free to see if its a good part. If it passes, then its your wiring or electrical contacts, which in order of diagnosis are always the first thing to check before replacing anything. If visible corrosion on of the terminals wire brush and see it starts charging. Also, wires tend to corrode from the inside out in that even though you don't see it visually it could be in the wire braiding. Sometimes its easier just to replace the wire all together especially if its all dry and crunchy.
 

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Discussion Starter · #10 ·
Sorry I haven't replied sooner. Issue is fixed! I had to put 2 washers on the back of the alternator. Issue was the large plastic shroud protuded past where I could have the cable mount flush against the alternator post. This caused the nut to back off and let the cable bounce creating a high impedance in the cable which heated it up and melted the plastic. With the cable now mounted flush against the post the battery charges normally now. Thanks to all who helped!
 
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