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Battery drain

After 06 mustang sits for about 7days, battery has to be jumped. What is causing this. I know it is not battery.

The title of your post says it all. Something is draining the battery. Look for a trunk light, glove box light etc that is staying on. If it is not one of those lights, you have to do a lot of work to track this down. A volt meter can be used to check the current draw of various circuits, it is a pain and a lot of detail work to find the culprit.

+1 to SteveCBT’s comment.
If the OP is not able to trace the battery drain himself, then I would suggest taking the car to a specialized auto electrical shop. There aren’t many of them, but they can be invaluable in a situation like this.

"I know it is not battery."

Excuse me Mr./Ms. Hawkeye, I’m not trying to be a jerk, but I think others will want this information, too…
why are you outright removing the battery as a potential culprit in this problem? Having this information with a little detail will get us moving in the right direction. Please explain the process of elimination.

Batteries dying too often can kill a battery. In addition to battery drain, good help here your battery could be toast also.

Disconnect the negative battery cable and let the car sit for a week. Reconnect the battery cable. If the car start, you have a current drain. If it doesn’t start you need a battery.

Here’s what I do first if this happened to me. After your last drive of the day, park, stop the engine, turn everything off, remove any battery chargers for cell phones, etc, get out of the car, and close all the doors. Remove the battery ground connector* and insert an amp meter in series between the connector and the battery post. It may read as much as 500 mA at that point. That’s just the power used by the computers in the car still running.

Now watch the amp display. The computers should go to sleep over the next couple of hours, and the current display should go down, and by 2 hours read no more than 50 mA. If not, whatever’s causing that, that’s likely the problem.

50 mA won’t run down a properly charged car battery in 7 days. Why?

Doing a little pencil & paper arithmetic, 50 mA for 7 days, that’s 8.4 amp-hours. 50 * 7 * 24 / 1000. Fully charged car batteries have 30-60 amp-hour capacity, so 50 mA won’t run down a good battery in 7 days. Best of luck.

If you feel lucky, you might not need to go through all this. See if you can figure out a way to check the glove compartment and trunk, if they remain lighted when the lid is closed.

  • Disconnecting the battery can have some unanticipated consequences. Search this forum for what they are.

Edit: Batteries can self-discharge themselves if coated with anything conductive, like spilled battery acid. Good idea to thoroughly clean the surface of the battery with a baking soda/water mixture when having this problem.

Yeah, all of the above. Like I said before, I’ve had two battery drain problems that I only found by accident. They were intermittent. One was from the door push button that turned the interior lights on. Coming out to the garage one night the lights were on and culprit found. But it only happened once in a while sitting. The other one was on the electronic level control that would short out. You had to be there with the test light while it did it to find it. If its intermittent, best you can do is keep testing with a light and if it gets bright, start pulling fuses till you find the right circuit but it can be hit and miss. If it is constant, easy to find.

I have to go along with common sense answer on this. You seem to be adamant that it’s NOT the battery so that begs the question of what makes you so sure the battery is not the cause?

Guys. Instead of yelling at the person who asked a sincere question, wouldn’t it be better to help her understand how it might be the battery?

I like @Triedaq’s suggestion as a first triage step. Disconnect the battery for a week and then try to start it.

I agree that it is probably a parasitic battery drain. But as others have stated, it could be just a bad battery.

But the battery, even if it was fine when this started, is in bad shape now. Each time a battery totally discharges, it suffers some internal damage. Do this more than a few times, and the battery will be toast.

You need to find and fix the problem, and then get a new battery.

"Guys. Instead of yelling at the person who asked a sincere question, wouldn’t it be better to help her understand how it might be the battery?"

? Who’s yelling? Please explain. Some of us are trying to understand more about the problem in order to sincerely better help.

Maybe I should have used the word “critical” instead of “yelling” when referring to Hawkeye’s assertion that the problem isn’t the battery.

We should welcome posters asking naive questions and making totally incorrect assumptions. The tone of our replies will dictate if they return or not.

The drain started with the first battery that came on car when bought it new. Bought new battery and drains also.

@Hawkeye22, do you mean that when this car was new in 2006 it had a battery drain problem.
You should have had this fixed under warranty when the car was still new.

If you mean that you bought this 2006 as a used car (new to you) recently, and it has had this drain problem from the start, I’d wonder if the charging system is keeping the battery charged.


This might prove very difficult to solve on your own without measuring the actual battery drain with a current meter. If you aren’t equipped for that yourself, finding someone who can do that for you is probably the next step.

I had a similar problem with a new VW Jetta. it was only a year old when I found the battery dead for the first time. The dealer replaced that one free.

But two years later it happened again, then again a year later.

I finally pinned it down, by trial and error, to the dome light. It stays on for a few minutes after you close the door. But sometime it would stay on forever (my hypotheses) and if it happened that I didn’t use the car for 3-4 days, that that was enough to drain the battery.

Just turned it off and left it off, and no problems after that.

My point is that tracing this down can be difficult. What I would do, to start, is go look at the car at night after it had been sitting for a few hours, and look for any lights.

@BillRussel The owner of a Lincoln had an even more vexing problem. He had a sloping driveway and when he parked the car backwards on his driveway the battery drained. In the garage nothing happened as well as being parked on the street.

One day he the car forward onto the driveway and the battery was OK. It turned out to be the trunk light switch on this car had mercury contacts which short circuited with the car on a steep slant. I don’t know further details, but a new switch solved the problem.

I remember Tom and Ray talking about the mercury contacts in the trunk light switch several years ago