jessicarabbit

This has to be one of the weirder things I've seen. I took my car, 2007 Mustang GT (Premium, if it matters), in to have two rear tires mounted and balanced yesterday. Today, I started up my car, drove it a mile to the gas station, and when I'm done filling up, the battery is dead.

When the key is not in the ignition, there was a ticking/knocking noise that seemed to come from behind the rear passenger wheel well, and as the last of the battery died, the sound seemed to turn into a whoosh. The sound seemed to go away when I tried to crank the engine, and would start again when I removed the key from the ignition.

What on earth could this be?! Any suggestions on how to diagnose or fix it? I tried searching around and couldn't find anything on it.

Urambo Tauro

Proper diagnosis starts with checking the battery via a load test. After that, the charging system needs to be checked. I've heard of S197 Mustangs having battery drain issues, but I've never dealt with them before. Do some searching.

That noise has me curious, though. I wonder if the purge valve might have something to do with it...?

jwog666

the noise is most likely caused by the module switching on and off again, this happens because the battery voltage is at the threshold required to operate the module. when you have a dead battery that has ,lets say, an 8v charge on a modern car, all sorts of relays and modules will shuttle on and off. ignore the noise and focus on the cause of the dead battery. charge it, test it, and then check the alternator as stated above.

Simon1

So you would need to get your battery tested and your alternator. Alternator may need to come off to be tested properly. That's pretty easy to do.

If your battery is ok, put it on a charger and let it charge up. If you have to replace your Alt, don't put it in the car and let it charge the battery. It's a good way to ruin your new alternator.

Good luck.

movielover40

My 2005 did same thing. Drove the car about 20 miles to warm it up before getting the oil changed and when I went to leave the oil change shop the battery was dead. Luckily there was an Auto Zone next door so I walked over and purchased a new battery and the oil change shop installed it. Something about these newer cars the battery just dies.

Chromeshadow

I wouldn't take it back to the tire shop for the battery, there are plenty of ways for a crooked shop to ruin a battery or alternator. I don't believe in coincidence.

jwog666

other than shorting the battery out with a wrench(which generally melts the lead terminals of the battery, or causes an explosion) or taking apart the alternator, there are no real world ways that a shop can sabotage those parts. sometimes chit breaks at weird times. i put a roof on my house a few years back, and as soon as i was done my refrigerator stopped working......weird but not related.

Chromeshadow

There is actually a ton of ways this is done, you can take one of the caps off and suck some of the acid out with a turkey baster, just leave the level low. You can add a little backing soda. You can loosen a battery terminal or the ground strap a little, if there is any corrosion you can even tighten it back down and your car will not start.
If you car is in for a couple of days, they can run the battery all the way down, leave it dead for a day before charging it back up. This is often death to a battery with a few years on it. I could go on, hope you get my point.

jwog666

yeah because it would serve a shop well to run a long term con to make $10 selling a battery(maybe) in a few days IF the customer comes back. if your terminals are corroded thats a problem to start and should be remedied. i have been working as a tech for 15 years and managed a shop for 5 and never in that time have i ever heard of someone trying to sell a battery or an alternator by sabotaging a car and hoping that they return later. (if i had they would have been fired on the spot) be paranoid, just not TOO paranoid.

the vast majority of trained professionals are not in business to rip customers off, how u can tell is if their business has been open for a few years, if it has its 99% a good place to go. the rip off artists dont keep their doors open long, because along with their ability to rip off people, they have no ability to properly repair cars and word spreads fast

Chromeshadow

Jwog, I never question your honesty, and I believe that most people tend to expect others to act as they do. Here is the link to the Midas investigation:

http://www.contracostatimes.com/sear...costatimes.com

Sear had a big investigation as well: http://www.nytimes.com/1992/06/23/bu...fter-flap.html

San Diego news teams removed one spark plug wire and took their car to about 10 shops, 9 of them submitted a bill over $600. One shop hooked it back up for no charge.

Here's the saying about auto repair shops in CA:

Will I get ripped off at my auto repair shop? Answer: look down-do you see *****?

People are much more qualified here in WI, and typically do not have to rip you off, but there are still plenty of shops that do. I could mention one large tire chain that has over 12 shops here in WI, but I'd probably get sued. After my wife made 7 trips for a simple wheel bearing replacement, I checked the work and one of the calliper bolts was not the correct bolt. They had stripped the threads and forced in a larger bolt. If this have fallen out while she was driving the left front brake would have probably locked up-sending her into on coming traffic.

I've run a repair service lab before, so I know when a shop and the people there are honest.That's one reason why I appreciate your comments and expertise here. Too bad we don't have more people like you in the world.