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Discussion Starter #1
The charging system in my mothers 2004 New Beetle Cabriolet started acting up last week (dash lights going crazy, engine chugging). I ran a few tests with my voltage meter and everything pointed to the alternator. A buddy of mine who has an alternator rebuild shop tested it and the output was all over the place. So he was able to get me either the 90amp which it already had or the higher output one at 120amp for $20 bucks more and he claims it should work without any upgrades to the cars wiring. I bought the 120amp alternator and installed this evening. I hooked my multimeter to the battery and it had a charge of 12.65 volts...good to go:). I started the car and the voltage immediately dropped to 12.14v:mad:...charging system still not working. I tested the voltage between the ground post on the battery and positive connector at the alternator and it was fluctuating between 12.80 and 13.90volts at idle so the part is working and its a wiring/connection issue. I decided to start back and the battery and check all of my connectors again and I realized I forgot about the fuse box ontop of the battery box. I open it up and the thick black alternator wire and the surrounding fuse is a mixture of melted charred black plastic...WTF?:eek:

Has this happened to anyone before? Did the old alternator cause this on its way out or could this be me adding the higher 120amp alternator instead of the 90amp one? I read on some other forums that it could also be the positive wire from the alternator and that it isn't of great quality?



 

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Wife's 01 1.8T mechanic
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I know this is hard to believe, but this is very common on New Beetles. It's also common for those green fuses to arc/corrode/melt. The cause is higher resistance due to corrosion/dissimilar metals. You need to change out parts, ensure all contacts are clean, protected with dilectric grease, and tight. More wonderful VW engineering...
 

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Discussion Starter #3
I know this is hard to believe, but this is very common on New Beetles. It's also common for those green fuses to arc/corrode/melt. The cause is higher resistance due to corrosion/dissimilar metals. You need to change out parts, ensure all contacts are clean, protected with dilectric grease, and tight. More wonderful VW engineering...
Really? wow. I was just over on Vw vortex and a few members were saying the same thing about other mk4's like the golf and the jetta too. Weird. I was thinking it might be a good idea to just head over to the parts sore a pick up a few feet of 2 gauge wire and redo that line running between the fuse box and alternator. Would 2 gauge be enough for a 120amp system?

Thanks
 

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Somewhat common issue.

Likely just a loose connection due to someone servicing the car not tightening the connection properly and/or heat and cold cycles causing the connection to come loose.

Not caused by your old alternator, heat is produced when the connection is loose and has too much Voltage drop.
 

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loose cable

Also check your negative cable of your battery where it connects to the chassis ground which is under the battery tray(poor design by vw) and most get lots of corrosion and no longer passes sufficient current. check the pictures I posted in the 1.8t section titled CAUTION of what I found. Good luck man
 

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Discussion Starter #6
Also check your negative cable of your battery where it connects to the chassis ground which is under the battery tray(poor design by vw) and most get lots of corrosion and no longer passes sufficient current. check the pictures I posted in the 1.8t section titled CAUTION of what I found. Good luck man
Thanks for the tip. I decided to check the two grounds. The one under the battery tray was covered in corrosion, but the one on the engine block was fine. The one under the battery block looked like it had never had any sort of protective coating from the factory applied to it. I gave it a nice application of di-electric grease and a couple of squirts of fluid film, should be good for the rest of the cars life.
 

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corrosion

glad u found a problem. The chassis grounding under the battery tray is the main wire coming from the battery and if it get's corrosion it'll loose continuity and won't pass sufficiant current to the connection in the engine block or any Negative connections, It's lilke loosing half of the battery and you have a floating ground (negative) not enough to charge up the battery correct or cuase the fuse melt up problem I believe.
 

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Ground Under Battery Tray!

glad u found a problem. The chassis grounding under the battery tray is the main wire coming from the battery and if it get's corrosion it'll loose continuity and won't pass sufficiant current to the connection in the engine block or any Negative connections, It's lilke loosing half of the battery and you have a floating ground (negative) not enough to charge up the battery correct or cuase the fuse melt up problem I believe.
That reminds me. I don't think I hooked this up when I had the tray out last. Where would I find it? Hmmmm... :confused: I think I hooked it to the transmission.

Would that cause trouble with my radiator fans?

It's 2AM and I'm going to go look at it right now!
 

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Ok

It's 2:30 and it was attached to the metal body under the tray. That ran to the coil pack it looked like. The wire did look like it had been repaired with one of those shrink tubes.
 

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Vag-com

I just have the free version VCDS-Lite and don't know if I can monitor temperature.

I did clean under the battery tray and noticed green corrosion on the cable where it connected to the body. I used some spray there.
 

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Burned Fuse box

I had the same issue with mine and after reading all these forums and have light issues, misfires, battery died, I have come to the conclusion that my 2002 NB Gl has a cheap Copper alternator wire. It cannot handle the heat. So it melts the fuse box where the black Alternator wire is and fry's other components. The fuse box gets hot, fans die, all sorts of things go wrong. Some have said to make Ur own 10 AWG solid copper wire (my is wrapped together with other wires but it can be done) then somehow crimp end to fit in fuse box. the Standard alt cable from VW is cheap copper mix. I wish I knew how to do it. But no one has uploaded directs, just ideas. I am not gonna buy a 2nd and 3rd fuse box and alt cable, when it doesn't address the real issue. VW is being sued is several states due to a lack of a recall on this cable issue. and if you take it in.$$$$$ just to here I don't know.
 

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VW wanted nearly $500 to replace mine. The wonderful independent VW shop replaced mine, last week, for $200, while I waited!

Find a reputable VW shop. Skip the dealer service.
 

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cable getting too hot

I had the same issue with mine and after reading all these forums and have light issues, misfires, battery died, I have come to the conclusion that my 2002 NB Gl has a cheap Copper alternator wire. It cannot handle the heat. So it melts the fuse box where the black Alternator wire is and fry's other components. The fuse box gets hot, fans die, all sorts of things go wrong. Some have said to make Ur own 10 AWG solid copper wire (my is wrapped together with other wires but it can be done) then somehow crimp end to fit in fuse box. the Standard alt cable from VW is cheap copper mix. I wish I knew how to do it. But no one has uploaded directs, just ideas. I am not gonna buy a 2nd and 3rd fuse box and alt cable, when it doesn't address the real issue. VW is being sued is several states due to a lack of a recall on this cable issue. and if you take it in.$$$$$ just to here I don't know.
:popcorn:
Sorry to hear you are having lots of problem with your beetle's electrical. I tried to tell folks in this forum before that just changing the melted fuse box does not fix the problem, you need to find out why it melted the fuse box in the first place................good luck folks :p
 
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