ALT fuse melted, plastic, not the element

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skimask
Posts: 103
Joined: Wed Dec 21, 2011 2:47 pm

ALT fuse melted, plastic, not the element

Post by skimask »

2005 Vibe base, bottom of the line model, 215K miles, good stuff...
Battery light comes on a couple days ago. 8v on the system. No charging... No kidding...
Get to looking... Find the 100 amp ALT fuse in the relay box by the battery kinda melted in there. The fuse is melted but has continuity. At the moment, I've got the fuse kinda mashed in there with some foam jamming the fuse in there between the relay box cover and the fuse box itself. There is no parasitic draw, battery doesn't die overnight, doesn't show any ridiculous draw with the engine running.

So...question is...
I'm looking at the wiring diagrams in the Chilton's manual, which by itself kinda sucks...

Question #1 - What is the correct wire gauge for the wire that leads from the alternator to the battery positive terminal?

Question #2 - I'm sure the 'rail' in the fuse box is pretty much toast as far as the ALT fuse placement itself goes. Getting a whole fuse box isn't going to happen. My plan is to bypass the OEM Alt Fuse with another 100 amp inline fuse that'll run between the alternator output and the positive battery terminal. Sounds good to me. Probably use a 50 amp fuse for testing since the only current going thru that particular wire will be charge current.
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joatmon
Posts: 10018
Joined: Fri Mar 21, 2003 5:19 am
Location: SMC MD

Re: ALT fuse melted, plastic, not the element

Post by joatmon »

I have edited this post as apparently, judging by your response below, you found it offensive, which was not my intent.

I apologize for insulting you by trying to help, and will not so injure you in the future.
Last edited by joatmon on Mon Oct 15, 2018 3:39 am, edited 1 time in total.
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skimask
Posts: 103
Joined: Wed Dec 21, 2011 2:47 pm

Re: ALT fuse melted, plastic, not the element

Post by skimask »

I started reading around these forums again over the past few days. Just what I figured. Straight down the shitter. Not much more than a bunch of posers buying garbage trinkets off ebay and adding sparkly thingies to the car mom and dad bought for them.

The '03 Matrix electrical diagram doesn't apply much to the '05 Vibe...especially under the hood. The feed side of the 100 amp ALT fuse, the copper bar, the rail, is burned. The metal itself is "burned". Anything low resistance in there has gone extinct years ago. The load side of the 100 amp ALT fuse is still just fine. The 'rail' no longer provides any tension for the legs of that 100 amp fuse to 'grab'. The only fix for this is to get a complete RELAY box. Not gonna happen. And since a person would have to basically rewire everything going to/from the RELAY box, it's a double-case of not gonna happen.

The fix in this case was a length of 8 AWG high temperature thick insulation multi-stranded wire with an inline 80 amp fuse running from the positive lead of the alternator to the positive lead of the battery...which is exactly what the 100amp ALT fuse in the RELAY box does.
I started with a 50 amp fuse...just in case. I ran the headlights for about ~20 minutes to kill off the battery and force the alternator to throw a buttload of charge at the battery, knowing full well that the fuse would likely blow in this situation. And it did. Then I tried a 60 and 75 amp fuse and repeated the test. All the while I had a FLIR E4 thermal imager watching the wiring to make sure it wasn't getting hot as well.
The 50 and 60 amp fuse blew almost immediately after drawing a headlight load off the battery for ~20 minutes. The 75 amp fuse blew after about 30 seconds. The 80 amp fuse didn't blow after doing that test 3 times, the last time drawing the headlights on bright for about 30 minutes, then starting the engine and letting it run until the charge current dropped to about 3 amps (~15 minutes or so). The wire never got hot, the fuse didn't blow.

Fixed.
zbyers
Posts: 1767
Joined: Thu Apr 03, 2014 6:12 pm
Location: Sheffield, Pennsylvania

Re: ALT fuse melted, plastic, not the element

Post by zbyers »

Rigged fixes; I like it! Just kidding, sorta. Hopefully it solves your problem, but doesn't cause others.
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