Alternator Main Fuse 150Amp Blows Again

[Jonwid]

The 03 GLS has a 150Amp alternator.

Twice now in less than one year, the main 150Amp strip fuse in the battery box has blown and taken out the plastic fuse box, melting and destroying it.

Anyone else have this happen?

I've heard that the main output wire from the alternator to the fuse box can become a source of too much resistance. How would one check this?

I should mention, the first time the fuse blew, I had a re-manufactured Alternator on the van for a couple of years. After that first incident, I attributed the blowout to that alternator, so I swapped it back out for the original VW alternator that I repaired (the voltage regulator brushes were worn out.)

[Jonwid]

I found this thread on the Vortex: There's an EV owner there who says he fixed this heating and melting problem with a homebrew 2-AWG alternator cable.

http://forums.vwvortex.com/showthread.php?4986219-Fuse-box-above-battery-melting/page2

The stealership has a new EV alternator fuse box in stock for $168!

Anyone heard of an alternator cable going bad and leading to this fault? How could a big guage copper stranded cable develop too much resistance as it ages? That just doesn't make sense to me.

Seems to happen a lot on other VWs with just a 90 amp setup.

[jjvincent]

It's a simple wire. Just one wire with no connections except on either end. If my EV did this, I'd pull the whole wire out and visually inspect it.

Usually when an alt wire has too much resistance, it just smokes the diodes or doesn't charge enough (real common problem on Porsche 911's)

[d-9]

Dont see how increased resistance in the altenator wire could lead to the fuse blowing - if it increases in resistance the wire will heat up, not the fuse...

Fuse should only blow if a load of more than 150A is applied to it, or if its got very old. I have no real idea how you could create a 150A load in a EV - a totally flat battery with a altenator working flat out should only create a 70-100A load. A big enough short to blow a 150A fuse would probably create a small fire...Im going with bad fuse, but interested if its something else.

[Jonwid]

Well I picked up the new fuse box from the stealership this afternoon😕.

Here's what the fried fuse box looks like.

And building up the new box.

I cleaned up all the brass lug connectors and even the fuse surfaces with a set of jeweler's files, got them nice and shiny. And I reassembled all with a good shmear of dielectric grease on all the metal binding surfaces and posts.

I will finish up tomorrow afternoon and then check it out for heating before buttoning it back up again.

[Abscate]

[jjvincent]

repeat

[jjvincent]

Replace the wire to the alternator. It's going to happen again. After seeing that picture, it's a classic case of overheating due to too much resistance and where it all necks down (the fuseable link) is where it runs the hottest. If you ever owned a VW from the 70-80's, you'd know in an instant that it's overheating (they always smoked the cooling fans and fuel pump circuit only at the fuse panel and not anywhere else). Audi changed this on the 5000 and thus, it smoked the connection on the back of the fan. Old VW's smoked the three prong alt wire only at the connection on the back of the alt, not anywhere else.

If my EV did that, I'd take the alt wire out, make a copy and then get a fuse block from McMaster Carr with an appropriate size fuse and put it next to the original box (you'll have to make a small jumper). Fuse and fuse box is a total of $13.

http://www.mcmaster.com/#9180k7/=12un4sc

[Jonwid]

[Jonwid]

Stealership wants $358 for a new "harness".

Outrageous, assuming that's just for the cable between the Alternator and the Fuse Box.

I found this on Amazon for about half the price per foot that McMaster has it. Mind you, I don't need 20 feet right now, but may be nice to have on hand for the travel trailer.

https://www.amazon.com/Premium-Extra-Flexible-Weld...tery+cable

Then, there's also these lugs:

https://www.amazon.com/Gardner-Bender-AML-206-Heav...lugs+3%2F8

Anyone have any thoughts about using these to make up a new alternator cable?

[jjvincent]

A NAPA or other parts store should have the terminals. Just do a youtube search on making battery cables. Honestly, I have made mine from copper tubing. All I needed was a hammer, drill and a hacksaw. Crimping is with a chisel.

I crimp solder all of my terminals and shrinkwrap the ends with marine shrink tubing. Everything from racecars to even my EV. I even did it when I overhauled my aux battery on my EV (with 2ga wire from the main battery to the automatic battery switch and even put a 2ga ground on it).

[Jonwid]

Cool picture, JJvincent! Based on what you suggested earlier, I have an idea to use 2 Awg or maybe even 1 Awg cable going straight from the alternator to the battery post with a separate fuse holder near the battery end of the cable.

I will power the new fuse box from the pigtail off of the battery side. That way, if there's ever another meltdown, it hopefully won't be in the original fuse box.

I talked to a car stereo builder this afternoon. They would build me a 2 Awg cable and fuse holder for $75, or a 1 Awg for $125.

[jjvincent]

I don't see any reason for anything bigger than 2ga. If you get too thick, the wire becomes too stiff and since the engine goes move in relation to the body, you want to have a bit of flex in the wire.

I used old 2ga BMW power cable for rewiring my aux battery in my EV. An e46 BMW has 15 ft of wire from the battery in the trunk to the jumper post under the hood, then another 2ft to the starter and then another 1ft to the alternator. That's 18 ft of wire just for the starter and alternator. Then it has 15 ft of 4ga running to the fuse panel. I can't imagine an EV needs any more than 4-5ft of cable to the fuse block.

I bet an e46 BMW draws more than a EV just because all of the other bells and whistles it has on it.

[Jonwid]

I decided to do the DIY alternator cable build. In addition to the 2AWG cable and lug rings, I have one of these crimper whacker things coming today.

https://www.amazon.com/gp/product/B003X51S00/ref=oh_aui_detailpage_o00_s00?ie=UTF8&psc=1

I'm going to do a test crimp and then cut through the lug to see if it "cold welds" the cable as it should.

I may just disconnect the original cable from both ends and leave it in situ while I route in the new alternator cable to the battery post.

[Jonwid]

So here is the new alternator cable install finished today.

2Awg cable with 5/16 copper lugs and a maxi fuse holder with a 175 Amp littelfuse.

Here's what I found when I cut the original 4 Awg cable out of the EV. See the burn marks inside center of the cable?!

Here's the new cable I built. 2 Awg with nice neoprene rubber insulation, and I added the PET woven wire loom on top.

Here's the new maxi fuse box mounted to the sidewall of the battery box:


Here's what the new cable looks like all installed:

Won't get to test things out until after I finish the transmission valve body refresh...which starts tomorrow!😦

[dixoncj]

On my 91 Westy, I ran a about a 6 or 7 AWG wire directly from the positive post on my alternator to the fusible link on my rear A/C. Reason being - this is a notorious melting point for Vanagons. It wasn't terribly thick, but seemed to be just enough to take some of the load off the inadequate main wiring on the van - because a Vanagon A/C can pull some real amps - especially as old as the blower fan motors are. Really cooled off the fuse area.
Since I'm adding a 150 amp to my EVC, I wonder if, rather than plumping in a new 2 gauge wire all the way through, if you could use a similar approach. Just keep my existing 4awg wire on the alternator and add on another wire to the alt post - and just run it to the battery post as well. Thoughts?

[Jonwid]

[Jonwid]

Well, the new 2 AWG harness directly between the alternator and the battery post appears to be very successful.

That's a good, strong volt reading there--at motor idle. Previously, the best reading I could get was barely 13 volts revved to about 2000 RPM. Definitely had a problem in that 4 gauge original wire.

Hopefully this one stays bulletproof and no more melted fuse boxes.

[dixoncj]

[jjvincent]

If that doesn't fix your EV, I'd sell it because it's obviously possessed.