Short in alternator loom, 100A fuse blows

[bongovi]

Hi Bongo crew. It's been a while!

She's been off the road for a good while, in need of a weld to suspension bits, and general rust treatment.

In that time the dead leisure meant the solar didn't raise the LB enough to flip over to the starter, so that died too. Borrowed a donor batt to get the engine running and did the classic reverse polarity dingdong mistake. Wondered why the headlights were coming on for a good 20-30 seconds... In that time obviously something else went.

Cut to two new batts in hand (LB+SB), connecting the starter and bam, 100A main fuse blows. Try a few more times, disconnecting things as I go, down to 2x100A fuses left... I'd better stop now.

Checked continuity in the dash fuse box (among others, all fine) and find the Engine and "Meter" (speedometer, lower left blue 15A fuses next to each other) are shorting. Disconnect the alternator supply and see the continuity has gone between SB pos and neg leads. So that's the issue. Take off the lead directly under the 100A fuse and confirm that's the one feeding the alternator.

Now, does anyone know what's best for next steps? Alternator itself could be shorting, loom could have melted somewhere in reverse polarity battery mistake, and still the mystery of why the "Meter" fuse socket gives a short signal. Although the last one's not such an issue if there's no short at the SB leads when alternator disconnected, right?

Thanks and a happy sunny Saturday to all.

[g8dhe]

Normally its the diode block in the alternator that is damaged and then shorts out the feed to the 100 Amp fuse. Normally quite a quick fix if you have a suitable alternator/starter repair shop local to you, mine was just 24 hours can't remember the cost but a lot cheaper than a replacement alternator.