# battery top fuse box heat issue - i'm down and not running



## mcTT (Oct 24, 2005)

Can someone run their car for 5 minutes and then feel the temperature of the big black 150amp wire that is in the battery top fuse block? My digital infrared thermometer says it is 220 degrees. My fingers say "ouch' that is damned hot. It is 150 degrees hotter than any wires in the car. 
I just put in an auxillary cigarette lighter socket and i have some realatively new guages. none of those wires gets hot. 
Is this normal or is my car about to burn up?
tia.


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## mcTT (Oct 24, 2005)

*update*

Update. Took out all my wiring for the guages and power socket. Still no change. Can't find any wires inside the car that get hot. I felt around under the dash as well. Maybe i need to take it to the dealer. Argh. 
Anyone else's car do this?


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## blackfnttruck (Jul 4, 2004)

*Re: battery top fuse box heat issue - i'm down and not running (mcTT)*

Never felt mine but I would have to assume, that is way too hot. Since it's a fuse without resistance it shouldn't get that hot. Are the connections to the fuse tight? Loose connections at the fuse will create a resistive connection and create heat.


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## mcttr3 (Mar 29, 2009)

*Re: battery top fuse box heat issue - i'm down and not running (blackfnttruck)*

Good idea. I put a socket on all the connections in the box and at the battery. All tight as a drum.


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## mcttr3 (Mar 29, 2009)

*Re: battery top fuse box heat issue - i'm down and not running (mcttr3)*

I tried the AC for a few minutes. The temp shot up to almost 300 degrees. Argh. I guess off to Sunset Imports. Unless I catch fire on the way ...


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## wreckedmyteg (Mar 23, 2006)

*Re: battery top fuse box heat issue - i'm down and not running (mcttr3)*


_Quote, originally posted by *mcttr3* »_I tried the AC for a few minutes. The temp shot up to almost 300 degrees. Argh. I guess off to Sunset Imports. Unless I catch fire on the way ...

I replaced the battery top fuse block 3 times, because the big black wire (which is the lead from your alternator) was getting so hot it actually melted the lugs out of the fuse block. The fuse never blew.
I think the wire itself is bad.
I replaced it with a new 4 awg run straight from the alternator, to an ANL fuse (150 amps), and straight to the battery.
It's not the fuse block....it's the wire. It's got to be.
























I forgot to upload my picture of it installed in the car to photobucket, but you get the idea.


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## mcTT (Oct 24, 2005)

*Re: battery top fuse box heat issue - i'm down and not running (wreckedmyteg)*

What did you do with the old wire? is it incorporated into the wiring loom when it leaves the battery top fuse box? 
I spoke wth a buddy who is a very good and technical mechanic. He was wondering why the alternator was sending so much current. I pointed out my battery is at least 5 years old and probably 8. He thinks the battery is dead or dying and the alternator is having to push a lot current to keep up. Thus the heat. I'll check the battery and then replace the cable.

Thanks again for your advice


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## wreckedmyteg (Mar 23, 2006)

*Re: battery top fuse box heat issue - i'm down and not running (mcTT)*


_Quote, originally posted by *mcTT* »_What did you do with the old wire? is it incorporated into the wiring loom when it leaves the battery top fuse box? 
I spoke wth a buddy who is a very good and technical mechanic. He was wondering why the alternator was sending so much current. I pointed out my battery is at least 5 years old and probably 8. He thinks the battery is dead or dying and the alternator is having to push a lot current to keep up. Thus the heat. I'll check the battery and then replace the cable.

Thanks again for your advice

I just taped of the two ends of the original wire. They don't go anywhere else, but to re-loom a new wire into the original harness would be a huge pita.
It's got nothing to do with the alternator sending out current. It's all about resistance at that spot.
I replaced my battery as well, and the thing melted the next day.
I can tell you 100% it's the wire, or the crimp on the end of the wire.
Also, the only way to tell how much current the alternator is "sending out" would be to throw an amp meter inline with it and the battery.
You'd think the fuse would pop if that were the case.


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## mcTT (Oct 24, 2005)

*Re: battery top fuse box heat issue - i'm down and not running (wreckedmyteg)*

Then the wire it is. Thanks much!


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## EuroStyle (Jun 24, 2000)

Didn't this cause a fire in Jeff Bipes' roadster?

Sean


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## mcTT (Oct 24, 2005)

*Re: (EuroStyle)*

I've been talking with him and he doesn't really know. My guess is we've just stumbled upon another serious design deficiency in the TT. It will be interesting to see if other people have a 'hot wire'.


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## 1.8Tabamoura (Jul 29, 2005)

My fuses don't get hot at all, the problem with yours is a bad connection just like wreckedmyteg posted , if you clean everything and redo the connections you will be fine. you could even solder the wires to the loop connectors if you thik the crimp of the wire is the problem.


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## wreckedmyteg (Mar 23, 2006)

*Re: (1.8Tabamoura)*


_Quote, originally posted by *1.8Tabamoura* »_My fuses don't get hot at all, the problem with yours is a bad connection just like wreckedmyteg posted , if you clean everything and redo the connections you will be fine. you could even solder the wires to the loop connectors if you thik the crimp of the wire is the problem.

FYI, it's not just TT's. I've got a GTI. I've also found the same problem with NB's.
I tried everything I could to keep that existing lead. I cleaned the connection with a wire brush, cleaned the lug with a wire wheel, and used dielectric grease. It didn't make a difference.
I suspect the crimp on the end of the wire was bad. Cutting it off and recrimping wasn't an option, because there wasn't enough extra wire, and it seemed like a bad idea to throw a splice in there.
I could have probably skipped the ANL fuse block, though, if I could find a ring crimp small enough to fit the fuse block. I might still try.


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## wreckedmyteg (Mar 23, 2006)

*Re: (wreckedmyteg)*

Did a quick search...
http://forums.vwvortex.com/zerothread?id=3383996
http://forums.vwvortex.com/zerothread?id=4362149
This one has a picture of the roadster fire;
http://forums.vwvortex.com/zerothread?id=4246796
http://forums.vwvortex.com/zerothread?id=4128408


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## mcTT (Oct 24, 2005)

*Re: (wreckedmyteg)*

Hey
i'd post over on AW but my account has been screwed up since they migrated the forum. I'm sure there are few toasty fuse boxes there. 
I sourced a Stinger Inline ANL Fuse Holder part no spd5203 from a car audio shop. Did you solder your 4 ga wire to the fuse holder or just use their set screws to hold the wires down? 
Is 4 ga big enough? The Audi manual says the wire size is 16 sqr mm which equates to about a 2 or 3 gage wire. Not sure where to get 3 ga.


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## wreckedmyteg (Mar 23, 2006)

*Re: (mcTT)*


_Quote, originally posted by *mcTT* »_Hey
i'd post over on AW but my account has been screwed up since they migrated the forum. I'm sure there are few toasty fuse boxes there. 
I sourced a Stinger Inline ANL Fuse Holder part no spd5203 from a car audio shop. Did you solder your 4 ga wire to the fuse holder or just use their set screws to hold the wires down? 
Is 4 ga big enough? The Audi manual says the wire size is 16 sqr mm which equates to about a 2 or 3 gage wire. Not sure where to get 3 ga. 

The factory wire looks more like 8awg. 4awg should be plenty big, and it hasn't gotten hot at all.
The Stinger ANL fuse hold I used uses ring terminals, not set screws.
You shouldn't need to solder, though.


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