Keep Blowing 80A main fuse

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gijoe985
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Keep Blowing 80A main fuse

Post by gijoe985 » Thu Mar 08, 2012 6:19 pm

I'm trying to help my brother with his 85 Toyota pickup. Sadly, I didn't help take everything apart, but he had to swap motors and now that everything is getting back together he is blowing his 80A main fuse every time he hooks up his battery. I think he said he also blew the fuse (maybe relay) to the ignition switch as well.

Any thoughts? I've done a bunch of electrical troubleshooting in the past, but for some reason I am drawing a blank on this. What could I do with an DVOM to help pinpoint where it is shorting?

BCLS776
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Re: Keep Blowing 80A main fuse

Post by BCLS776 » Thu Mar 08, 2012 8:48 pm

Start by having a look for wires around the engine compartment that got pinched or roughed up during the engine swap. It sounds like it is on the main power wire to the fuse box or starter and it is probably shorting on the chassis. Make sure the wiring got correctly reinstalled on the starter too.
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Mmfh
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Re: Keep Blowing 80A main fuse

Post by Mmfh » Sat Mar 10, 2012 10:29 am

Make sure a ground and hot didn't get switched on the alternator. Follow main hot down to the starter and make sure it isn't pinched anywhere.

gijoe985
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Re: Keep Blowing 80A main fuse

Post by gijoe985 » Sun Mar 11, 2012 10:14 pm

[QUOTE=Rh1n0_86OneTon;3800873]Put the meter on Ohms and measure from the + battery terminal (not hooked up to the battery) to ground (black wire from battery screwed to inner fender right at the battery).
It will read as a short = very low Ohms, like 1 or 0.something. Start removing things from the circuit. Disconnect the starter first at the starter. Keep checking for the Ohms to jump up. Yank fuses until it does. When it does rise, you will at least have a place to start tracing the short from.[/QUOTE]

This method worked great. An alternator wire was grounded. Thanks!

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