Reversed Battery Leads - Ford Mustang Forum
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post #1 of 5 (permalink) Old 3 Days Ago Thread Starter
g00f's Avatar
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Reversed Battery Leads

My old battery was in need of replacement, and I have another coming in but in the meantime I was trying to swap in a spare from our Jeep so I can get to work tomorrow. Working in the dark, I did not realize the terminals on the battery are essentially mirrored from the previous one, and hooked them up backwards.

This doesn't seem all that rare of an occurrence, but where this gets wonky is my car has an amalgamation of original style wiring coupled with the wiring for a Duraspark II ignition.

When I hooked up the battery I noticed smoke coming from the general location of the alternator. I disconnected the leads and realized my blunder. I then correctly orientated the battery and decided to try and hook it up correctly to see if anything would work. Upon hooking up the leads correctly I was once again greeted by the smell of burning electronics, and after a few seconds a notable pop from the direction of my voltage regulator. Guessing that's toast now.

Going to wait until I have some daylight this weekend to asses what all I've fk'ed up, but does anyone have any input on what to be on the lookout for? is my alternator gonna be done for? Should this just be the final straw that makes me wrap up the inventory collection and finish up the upgrade to a modern alternator(I've had the kit sitting on the shelf for awhile now but never wanted to tear into the electronics)?

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post #2 of 5 (permalink) Old 3 Days Ago
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Chances are the alternator and VR are probably toast. Also check the alternator output wire and any fusible links and fuses where circuit power is missing.

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post #3 of 5 (permalink) Old 2 Days Ago
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The amalgamation of wiring may have somehow omitted a fusible link which is supposed to protect your alternator, regulator and other electronics from just such an event. Accidentally connecting jumper cables reversed can cause the same problems. The initial reversed battery connection probably damaged some wire/cable insulation resulting in a short that caused additional damage when the cables were reconnected the correct way. If indeed there's no fusible link in place it'd be really good idea to install one as a part of the repair.

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post #4 of 5 (permalink) Old 2 Days Ago
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I've been there. Had to replace the charging system, but everything else seemed to be fine. I think I was running a Pertronix Ignitor at the time. If it doesn't start after you've replaced the charging system, you'll know the Duraspark is fried.

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post #5 of 5 (permalink) Old 20 Hours Ago
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Unless you added it yourself, no one had even thought of using a fusible link for a 60s or 70s car. Once you connected the battery backwards you very quickly fried the diodes in your alternator. Since diodes are damaged nearly instantly I am not sure a fusible link would have helped even if one had been installed. They are simply a short section of smaller wire that melts like a fuse. The wires inside an alternator are smaller than any fusible link and would melt first. Diodes melt even quicker. A typical mechanical voltage regulator will work with either polarity but if you had a solid state one you probably fried it as well as the alternator. Once damaged there is no recovery for anything solid state.
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