Beetle TDI Battery Fuse Box Melting

[Nick1994]

The Beetle has been sitting for close to 2 months in the garage, hibernating. I noticed it cranked a little slow so I checked and the battery was at 12.0V. I decided to drive it over to O'Reilly Auto Parts for a battery and alternator test. Once I took off the battery cover I noticed a wire was super hot and that things started melting, such as that fuse there I pulled out. They put their tester on and it said battery was good, just low. Also the alternator failed to charge.

The black wire seemed the hottest.

It's being towed to my VW mechanic right now.

Anybody have any ideas what it might be?

 

[spasm3]

I would have to wonder if the voltage regulator was the cause of this. I don't know a lot about VWs , is the regulator separate or integral to the alternator?

Btw i can't tell if its just the lighting, or is that green corrosion on the first red wire from the left?

 

[spasm3]

Another thought , did you own this car since new? Any chance it was a flood car?

 

[Elevguy]

Poor connection

 

[sleddriver]

Melted insulation is a sure sign of a high resistance in a high current flow circuit. That corrosion there is telling you something. Those end connectors will have to be redone.

 

[Nick1994]

Originally Posted By: spasm3
Another thought , did you own this car since new? Any chance it was a flood car?
Yeah it looks like corrosion.

My aunt was original owner, never been flooded.

This is actually the first time it's been on a tow truck due to a mechanical breakdown.

The only other time it's been on a tow truck was almost 10 years ago a semi-truck's tire tread got flung into the windshield.

 

[Nick1994]

More background that may be helpful is:

Battery was replaced earlier this year in the early Spring by the dealership.

I replaced the alternator earlier this year too and it's from O'Reillys. The previous alternator was an O'Reillys and had a little bit of a noisy bearing.

 

[dishdude]

For the wiring to get that hot, I'd think something would have to have be shorted directly to ground.

 

[Mr Nice]

I thought you were selling the VW ?

 

[qjohn]

If it melted just near that destroyed fuse, then high resistance connection likely mmcaused it -- a gapped connection. If it got hot in the lower right hand part of the first picture, then probably there is a circuit board inside that burned. Either Way, a new fuse box should fix it.

 

[Nick1994]

Originally Posted By: Mr Nice
I thought you were selling the VW ?
I will be soon. Have been waiting for over a month for the lien release from Wells Fargo. The car was paid off over 5 years ago and they never sent it or a title. We went down there and requested it and they said it'll take 3 days. Over a month later and still nothing.

 

[stephen9666]

Problems with that battery fuse box are common in this car. My wife's beetle never had the issue, but I read about it online.

Do some googling on the VW sites for more info.

 

[spasm3]

Originally Posted By: stephen9666
Problems with that battery fuse box are common in this car. My wife's beetle never had the issue, but I read about it online.

Do some googling on the VW sites for more info.


The common fix seems to be a new alternator cable to the box, and if melted a new fuse box.
IF i had one of these models, i would change that cable proactively.

Here is what i found when searching.
http://newbeetle.org/forums/questions-is...new-beetle.html

 

[The_Eric]

Common enough that Dorman makes a replacement for it.

 

[Nick1994]

Originally Posted By: spasm3
Originally Posted By: stephen9666
Problems with that battery fuse box are common in this car. My wife's beetle never had the issue, but I read about it online.

Do some googling on the VW sites for more info.


The common fix seems to be a new alternator cable to the box, and if melted a new fuse box.
IF i had one of these models, i would change that cable proactively.

Here is what i found when searching.
http://newbeetle.org/forums/questions-is...new-beetle.html
Wow! Thanks for that. That looks exactly like the issue. I'll be interested to see if the alternator or battery turns out bad. Both are under warranty so if the alternator shorted this out, O'Reillys will be getting the bill. If the battery caused this, VW will be getting the bill.

 

[JHZR2]

If the alternator is not charging, off the car (since we don't know what kind of and how good of a connection those wires are making), then I'd wonder if a shorted diode allowed a ton of current to rush back into the alternator, before something acted like a fuse and opened up. Bad diodes in an alternator can discharge a battery to zero. I had that happen once. But if the circuit created by the failed diode is high resistance, the current naturally limits. If on the other hand, the circuit became a hard short, the battery could source a ton of current and cause stuff to melt before some weak link naturally became a fuse and opened.

What makes me think twice though is that fuse. Why would it blow? It's only 10A. Or did it blow? Did it just melt?

A hard short that is stopped by something opening up creates a high L di/dt (inductance x change in voltage), and if that cable run is long enough, it can store a decent bit of energy. So when whatever else opened up, the bussing in that distribution box all got a voltage spike and the circuit with that fuse perhaps absorbed it?

 

[Nick1994]

My Camry's battery reads at 13.1V when off, I've suspected there to be a problem with it so I took it to O'Reilyls afterwards and that same tester said the same thing, "Battery OK, needs to be charged. Alternator Failed" even though the Camry alternator is obviously charging since the voltage goes to over 14 volts while running and the battery is obviously not low.

I'm questioning their scanner and will get my Camry tested tomorrow at another location.

The VW will be further tested at my VW mechanic tomorrow.

I also don't know if that fuse blew. I removed the fuse because I could see the black burn on it so I pulled it out (with pliers) and saw that it melted the fuse block. I stopped there and decided not to drive the car and called a tow truck.

 

[asand1]

I replaced many of those boxes working for VW/Audi group. It is from high resistance/corrosion at the connectors. replace the box and harness, make sure all connectors are clean, use dielectric grease on the push in fuses, and spray the buss bars.

 

[DriveHard]

Its the self destruct mode so it can't be tested for emissions. Did you get it close to an emissions testing station?

 

[edwardh1]

I had a 79 rabbit that had a factory recall on a pattern failure of a burned wire/terminal inside the fuse box.
the factory fix was a 8 inch long jumper wire around the fuse box.
Maybe VW has the wrong amperage vs wire size needed charts for electrical work???