Battery draw could be from fuse, alternator

By Douglas McAlister

Q. I own a 2006 Mustang convertible with 30,000 miles. I love the car but if I leave it for more than four days the battery goes dead.

There is a website that shows other people have the same problem on 2005 to 2008 Mustangs. I have done my own investigation as trunk lights, doors left open, etc., with no luck. Now I just shut everything off. Ford is not any help. Any ideas?

A. There are two possibilities here. Something is drawing the battery down or the battery itself is bad.

You did not state whether or not you have replaced the battery or if it is original. If it is original, it is time to replace it. It’s a 7-year-old battery and that may be the whole problem.

If it is new or if you still have a problem after you replace it, you will want to check the system for a voltage draw. After one hour, there should not be any draw over 50 milliamps (.05). Anything over that is too much and you will have to isolate from where the draw is coming.

There are two common culprits on this car that you can check first. One would be the audio system fuse, No. 31.

The other thing to check is the alternator. Disconnect it and see if the draw goes away.

It is also possible you have a module that won’t go to sleep. If that is the case you will need to work through a scanner to figure it out.

Regardless, there should be a solution to this problem and a good diagnostic technician will be able to figure it out.

If you do end up replacing the battery, be sure to buy a good one. Get a good Interstate Battery or a Motorcraft Battery, but I recommend you stay away from a cheap one from one of the big box stores. Let us know what it turns out to be!

Ÿ Douglas Automotive is at 312 S. Hager Ave., Barrington, (847) 381-0454, and 123 Virginia Road, Crystal Lake, (815) 356-0440. For information, visit douglasautomotive.com. Send questions to underthehood@dailyherald.com.