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Car won't start, battery and alternator are fine...what could it be?

Hey guys,
So 3 times in the last 2 days, my car has needed a jumpstart. Took it to pepboys and they told me to replace the battery, a new battery later, my car wouldn’t start again and I needed to get it jumpstarted again. Took it back to pepboys, they say everything checks out fine including the battery and the alternator and that it should work fine. This happens to be exactly what they said the last time.

Now the extent of my knowledge ends here, so I’m looking for suggestions on what it could be, what to do or any other advise you could offer. This is my first car so not greatly experienced with cars.

The car is a 2012 Ford Mustang V6 convertible.


Is the car is still covered by the Ford factory warranty? If so take it to the nearest dealer.

If not a dealer take it to an independent mechanic. Avoid chain repair shops.

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Unfortunately it’s not covered by warranty, warranty lasts 36000 miles and mine has run 40000. Right on cue;). I guess I gotta try an independent mechanic, so pep boys are no good?

If by not starting you mean the starter motor is not engaging and physically turning the engine over and there is no “click” sound then the problem could be in the range selector switch or the anti-theft system.

You could try shifting into neutral and attempting a start when this problem occurs and that may (but it’s by no means a certainty) point to the range switch.
The car is a bit young for a range switch problem but the possibility is always there.

Explain what you mean by “it won’t start”. Does it cranks ok with the key in “start”, but won’t catch and run? You know, does it make that rrrr rrrrr rrrr sound before the engine starts running on its own? Or does it refuse to even crank, maybe just a click, or no sound at all with the key in “start”?

No it doesn’t crank… The electronics turn on but turning the key does nothing… I can’t remember if there was a click… Ill check on that and report back… I disconnected the battery overnight to check if its an issue with something discharging the battery… Could it be a spark plug issue?

Well, you know a spark plug isn’t part of the starting system. You want to know why the engine doesn’t crank. If it isn’t an ignition switch it could be a bad ground.

If your battery terminals were cleaned, read on. If not, have them cleaned and when that doesn’t work…

On the old Fords the negative battery cable was a major thing. It grounded the engine to the battery as well as the body/frame. That cable may have a lug (tab) on it with a bolt through it which grounds it to some metal. If you have that cable you might just loosen the bolt a little and retighten it. When cars were made of steel, the “extra” lug was 6 to 10 inches from the negative terminal.

To test for that particular ground problem, connect a jumper cable from some metal on the engine to the negative battery terminal. If engine starts, you found the bad ground.

I’m guessing this bad ground test only works when the car actually doesn’t start, and it seems like thats the crux of the problem

My suspicion is that its a bad ground, now the only thing is that the mechanics at pepboys say they will have to do an electrical diagnostic to figure out what the issue is…considering they charge 100 bucks an hour…anyone have an idea how long it takes to do a diagnostic on a 2012 ford mustang v6?

thanks for all the answers guys, this is helping

CORRECTION. I should have posted connect jumper cable from metal on engine to metal on body or frame. The other way is to diagnose a bad negative cable. Small difference and wrong may work too because sometimes anything can help. Good grammar there.

Your car isn’t old enough for the cable to deteriorate but you never know.

You not only reached the limit of your knowledge, but also of Pep Boys. As a general rule it is a good idea to avoid getting general service and repairs from national chains. Look for a local mechanic, the best ones will be extremely busy because people have found out they do goog, honest work at fair prices. That doesn]t necessarily mean cheap, there is a huge overhead in running a repair shop.

If your Mustang doesn’t have a voltmeter, buy a digital one you stick in a 12V socket. Make sure the meter reads greater than 14V whenever it’s running. You’ll gain useful info to aid troubleshooting. If the socket doesn’t turn off with the key, remove the meter when the car’s not running.

thanks guys, nearest mechanic is about 20 miles away:( and down here near miami they dont speak english even…but yea the big chains have proven to be quite useless for more detailed work…

For a no-crank problem here’s what I do.

  1. Clean battery posts and cable ends with a battery post cleaning tool.
  2. Load test the battery.
  3. Fully charge the battery.
  4. Battery passes load test and battery posts bright as a new penny, the battery is fully charged, and it still won’t crank? Then the next thing I do is measure the voltage on both terminals of the starter motor during an attempted crank (key in “start”). Voltage is measured from the terminal on the starter motor to the starter case, with everything connected. If both are above 10.5 volts and the starter motor doesn’t crank, the problem is most likely with the starter motor itself and it will need to be replaced or – usually the better choice – fixed at the local auto-electric shop. If either is below 10.5 volts, work backwards from there to find out why. There’s some higher than normal resistance connection somewhere between the ignition key and the starter motor.

Note: I have an older Ford, on that truck there’s separate starter relay; i.e. there’s only one terminal on the starter motor. I’m not sure if Ford still uses that configuration; on most newer econoboxes, the starter relay is part of the starter motor itself. If your car uses a separate starter relay, that’s where the second “starter” terminal is located. It’s for the “start” signal from the ignition switch/neutral safety switch.

Could be your neutral safety switch. On this car it is a neutral safety switch/range sensor per Rock Auto.

Hard to understand how jump starting would help if it was the safety switch. But it’s possible I guess, if the switch was still sort of working but had higher than normal on resistance. Or that when jump starting maybe the OP is doing something a little different with the transmission controls and this moves the switch into the correct position.

You are right, the fact jump starting works rule out the neutral safety switch, brain fade on my part.

Hey guys I have a question I have a 02’ Mercury mountaineer and I just replaced the battery and the alternator but it’s still won’t start, the starter clicks, lights, window, radio everything works just won’t turn over any ideas what it could be?

@Noah_Nunez , suggest to repost your car’s problam as a new topic. Click “maintenance/repairs” above left, then “new topic”, above right.

Anyone got a clue why my 12 Camry se will not start has new battery new terminals and also alternator will turn over when start button is pushed but will not fully start jus keeps turning over I have checked the fuseible also looks well I’m stumped