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My car turns off before it starts up

I just recently bought the mustang (07 v6), and when at the dealer, it was dead. Reasonable, as cars aren’t moved too often. So the salesman tells one of the mechanics to bring the battery charger to give it some juice, and the car then turns on as soon as i turn the key. Now however, something weird happens. Instead of turning on, the car dies, or at least i believe it does (stereo and dash loos all light, and stereo resets time). I hear the crank sound once, and then the lights go out, dash and stereo and all. but then it suddenly starts cranking up again, and then turns on. Could this just be a battery problem? or can it be something else?

We don’t know where you live or if your inspection problem was solved. Many states allow AutoZone and other parts stores to check codes and check batteries and alternators. That should be your first step because a new battery would be an easy fix. Most likely this was an ‘As is’ purchase so a mechanical inspection might be worth while, about 100 to 150 dollars .

It sounds like you bought a car with a dead battery.

Replace the battery and report back.

Tester

Or it’s possible the battery remains serviceable, but the battery posts and connectors need to be cleaned up. Try that first before springing for a new battery.

The current demands during cranking are not steady, but instead pulsate as the starter motor turns. So what could be happening is during a high current demand pulse the battery terminal resistance is high enough it drops the voltage too low and the starter motor stops turning. But it has enough momentum to move to a position where it doesn’t require as much current and starts turning again.

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You need to drive the car for a while after a boost…the longer the better so the battery can fully charge.

In addition to the other replies, I have to wonder whether the OP’s car came with the traditional 30-day warranty on used cars, or if it was bought “as-is”.

It’s better to charge the battery in the vehicle rather than rely on the alternator to charge the battery.

Doing the latter can fry the alternator.

Tester

Update: I cleaned any of the corrosive stuff on the terminals, no change, drove it around for a while, no change, but i did end up getting stranded at a gas station. I just went to go charge the battery, but as it turned out, It has a dead/bad battery cell, so I just bought a new one. It now starts up perfectly normal. Thanks for the help though guys! helped isolate the issue

Sounds like you are back on the road with a new & reliable battery. Thanks for the update. Do you know how old the failed battery was? Most batteries start pooping out at the 4-6 year range. In hotter climates, 3-4 years. The date it was manufactured is often labeled on top of the battery.

This was a used vehicle. What difference does it make the age of the dead battery anyway.