excessive current pull?

1048 Views 7 Replies 4 Participants Last post by SueBrew, Apr 5, 2019

SueBrew

Discussion Starter · Mar 30, 2019

I've often wondered why my Forester sometimes starts fine, and then I'll leave it parked for a 10-15 minutes while I go inside a store or something, and then get a weak ignition chime, and no dome or courtesy light, followed by a no-start. Well, today, after happening for the umpteenth time, I saw something pretty bad. The battery inlet side of the main 80 amp fuse was blistered from heat, and the plastic got so hot that if melted not only the fuse casing, but also the fuse box casing. I have a feeling that my ABS system might have a part to play in this problem. I put in another 80 amp fuse just to get me home until I could start tackling this problem on the weekend. I have a 2005-2009 Legacy alternator installed, that puts out 110 amp instead of the stock 80 amp alternator, but I don't think that makes a difference, because that is only the amount of available current, not how much current is being pumped through the
car's fuse. What really surprised me is how hot the link got, without blowing the fuse. Any type of known electrical issues to test for first?
thanks.

jb.

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2.5x_sleeper

· #2 · Mar 30, 2019

@SueBrew my first thought, the SBF-1 fuse mounting nut is loose?

I've seen many forum member upgrade to higher output alternators with no issues.

Bobby...

['07 FSXT MODding Journal] ['03 X MODding Journal]

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SueBrew

Discussion Starter · #3 · Mar 30, 2019

Thanks for replying Bobby, the mounting nut was secure, but it is weakened due to the continual excessive heat that went unchecked. In addition, the underside mounting bolt is now also a little wobbly, so I did not tighten the nut very tightly. Like I was saying, the alternator might not be the problem after I thought about it for a while, but could a loose or rusted ground connection somewhere else be causing the excess current draw??

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2.5x_sleeper

· #4 · Mar 31, 2019

@SueBrew a couples thoughts...

[1] I would assume the SBF-1 fuse would blow before there was that kind of heat damage!
[2] Why is there only heat damage on one side. If a high amount of current was passing thru the SBF-1 fuse, it would be hot on both side. This is why my first thought was a loose SBF-1 fuse mounting nut. A loose nut = resistance = heat!

Bobby...

['07 FSXT MODding Journal] ['03 X MODding Journal]

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SueBrew

Discussion Starter · #5 · Apr 4, 2019

Bobby, Since my ABS light flashed intermittently, and was involved at the same time the BRAKE and battery icon light faded in and out together. I did some digging around on other forums, and it looks like a guy on one of the legacy/Outback forums traced his issue to the ABS ground wire, which is connected to the power steering pump. In the meantime, as a temporary measure, I disconnected the main 20 amp ABS FUSE in the interior fusebox, in the hopes that the problem will not return, and so far, for 1 week, the car has since not stalled or got a low charging indicator. So I'll check that, and also one of his taillamp brake bulbs, even though operational, had a minor short circuit in it. He tested the bulbs all one by one, but I don't have the patience for that, so I'll just replace all the bulbs with new ones. I'll keep it updated.

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smiffy6four

· #6 · Apr 4, 2019

The nut on the left side of the fuse looks like it is suffering from the green death, aka corrosion. pull both nuts, clean everything up. The fact that it only melted one side, indicates a dirty, high-resistance connection.

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RyanT

· #7 · Apr 4, 2019

Agree with all of the above... melting has to do with the current density. If corrosion was reducing the actual conductive area there, it would melt just there. Same logic applies to kinked wires melting at that point, etc...

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SueBrew

Discussion Starter · #8 · Apr 5, 2019

Thanks, if there's anything that you Canadians have a good eye for, it's definitely corrosion. 😉 Another thing, the underneath bolt on that nut is wobbly, and I have a feeling it should also be replaced before it snaps off. Do you guys have any experience with pulling the entire fuse box out and re-installing that hardware? Anyone have an exploded diagram to help?
I'm still going to check the ABS ground wire, does anyone know where in the engine bay chassis that it is grounded? Any pics? Thanks for all the help guys.

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excessive current pull?

SueBrew

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