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· Tech Advisor
2006 Mustang GT Deluxe
58 Posts
If I had to take a wild guess about this, I'd say that the battery is not fully secured, and it's arcing from the positive terminal to some grounded part as it moves around. When that happens, you get a dead short, and yep, that'll sure kill an alternator!
I never would have thought of that, but wouldn't it also fry the ECU if the battery positive terminal was arcing to the firewall?

Have a 2006 mustang gt with about 90,000 miles currently, bone stock. For some reason whenever I do a hard pull or heavy acceleration my alternator fails and battery dies eventually. I'm currently on my 3rd alternator and the last one I bought was from autozone (duralast gold 135amp). I haven't yet done a hard pull since I've changed it out. Any help will be appreciated.
I'm going to take an educated guess and say that the alternator voltage regulator is failing. It's possible that when you rev the engine high, the alternator is overcharging the battery. A simple way to find out is to measure the voltage across the battery terminals at idle and observe it as you slowly rev the engine up to 6000rpm.
The stock alternator has a clutched pulley to prevent this from happening. If yours doesn't, that could be the underlying cause of the voltage regulator failing. Another remedy is to install underdrive pulleys since these will slow down the alternator by 25% (there are no issues associated with these on a 3V GT).
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