draexo

Hey there.

I have a problem and I do not know how to troubleshoot it.
I have a 2012 Mustang v6 convertible. There are a few minor cosmetic mods to it and two electrical mods.

In the last several weeks the battery keeps dying and I need to charge it in order to start the car. The longer it sits, the greater the chance of it dying.
This week was especially bad as the kids were out of school and we stayed home, not taking the car anywhere. Let it sit 36 to 48 hours and it will not start. If I drive the car daily I do not have this problem.

I took it to a car place and they brought out a machine that they hooked up to the battery for a minute or two and they tell me the battery (stock battery) is fine. This had me thinking it was an electrical drain.

The two electrical mods are underneath lighting and subwoofer/amp.
I completely disconnected the underneath lighting and the problem continued.

At this point, I thought it was the subs. I measured my AMP draw at 1.2 MICRO AMPs (0.0000012 AMPS) with the car off . I figured this could not possibly be draining the battery. I then took the AMP meter to my other car, a 2012 Chevy Traverse, and I show the AMP draw as 0.0000012 AMPS as well. I just did this as a comparison.

My question is: What is a normal AMP drawn for a Stock 2012 Mustang. I have read it is .05 AMPs. Any idea how I can figure out why the battery keeps dying when the car sits for a day or two? If I drive it daily, this problem does not occur.

Any suggestions appreciated.

Dre

Lem-06

Just as a easy check, get the alternator tested.
My 06GT didnt start monday morning, charged and it started fine, didnt start at lunch, jumped and ran fine, charged it before i went to work that afternoon, after work it BARELY cranked. took alternator to autozone the next day and it came up bad.

It seems it would put out enough to run the car/my other electrical goodies, but it couldnt top off the battery.

Art161

Is your battery sealed or can you check the cells? If you can check the cells, use a battery hydrometer to ascertain the state of charge of each cell. If none of them is near full charge, I would suspect a bad alternator or a bad connection. If some cells have an acceptable level of charge, but others have a low level of charge, then it is a bad battery.

I have a difficult time believing the low parasitic draw you are measuring. Typical would be 20-50 milliamperes.

draexo

I have a hard time with the amp draw as well. It is a brand new just out of the box meter and I think it might not be working correctly,which is why I tested it with my Traverse as well. I was checking voltages and when not connected to anything the meter was reading 300plus volts DC. When I connected it to the car I was getting 12.6 volts DC. Now I wonder if the meter works at all.

So best next step is to check alternator? The guy at Autozone said if I remove the negative terminal while the car is running and it keeps running that the alternator is fine.

steel pony

Since 2006, the alternators have been a known weak point on the Mustang.
The first obvious thing to do is turn off everything when getting out of the car. These cars are also very prone to drawing current (even if its a small amount) to keep certain things operational on the car. The radio and CD players are one of these, especially with the 13+ models, since you can get in the car and operate the radio without turning the key. Putting additional things on the car, such as aftermarket lighting and radio equipment can increase additional draw/strain on the system, thus resulting in shortening the life of the "not so great" alternator.

Some will fail, some won't...such is the life of an electrical component.

TBH, you have a 2012, so if it's not over 36,000 take it in and have it checked under warranty. Chances are that if it is the alternator, you're going to be down for 3-5 days just waiting on the part.

Also, since you are running additional aftermarket electrical equipment, you may want to invest in a better aftermarket alternator.

Art161

The guy at AutoZone is a moron for suggesting that. One of the purposes of the battery is to clamp down on voltage spikes. You can fry the electronics if you have the engine running and disconnect the battery.

Lem-06

yea dont listen to him.

After i installed my cams i could see the engines lope via my dome lights if they were on. Always knew the alternator would go it just took a new stereo installation and a few months to finally kill it. New alternator, no pulsing in the dome lights and it charges fine.

draexo

I think the AMP meter was bad. I am getting a new one. Someone I know who is a mechanic says he is almost sure it is the aftermarket subs based on his experience. I am going away for the holiday and will follow up once I know something better. Thanks for all your advice!

draexo

Ok. I am back from my little trip out of town. The car sat for 4 days. Normally this means it would never start. It started right up. I removed the "remote" power wire from the battery before I left. This is the wire that turns the subs on and it does not supply them direct power. My assumption is that it is turning the subs on somehow.

I am going to move this wire to a fuse that has no power when the ignition is off. Locally I can only find the small micro fuse taps. Any idea which one would be a safe bet to attach this remote wire too?

Lem-06

seriously your remote on wire was directly to the battery?

the point of it is to be fused with IGN on source, not always on. problem solved