Ford Mustang Forum banner

2005 Mustang GT Charging Issues

6274 Views 12 Replies 6 Participants Last post by  AlaskanWookie1
Hi all,

I am new to the site and I am looking for some help with an issue I am having. I have a 2005 Mustang GT with an automatic and a Shaker 500 sound system.

The issue I am having is dealing with the charging system/battery. I never had a problem with it starting until about 1 month ago. The car turns over very slowly and acts like it is not charging. I have no warning lights on in the dash or anything. My charging gauge is working fine as well.

I bought the car used and had the alternator replaced about a year ago along with the battery (Both Motorcraft) under the dealers warranty.

The slow starting problem will go away if I drive the car for long distances without stopping (20 or 30+ miles at highway speed) but if I am sitting in stop and go traffic or only drive the car for 15 or 20 min the problem will come back. I just got back from a 2000+ mile trip and had no problems, but as soon as I went from my house to work and back (6 miles) the slow starting problem came right back.

I had Ford test the battery and they said it was fine. The battery voltage read 12.6v.

Has anyone had this problem or know of someone who did? If so, do you know how to fix it?
1 - 13 of 13 Posts
Sounds like the alternator isn’t putting out normally. Sometimes a poor connection can do that too. One thing you could try is cleaning the battery posts with a wire brush then immediately reinstall the lugs before significant oxidation can set it. You could also check to confirm the main cable is properly tightened on the alternator too.
Cool. I will try that tomorrow after work. I pulled the radio fuse and amp fuse for now. That helped last time. I am thinking it is some type of grounding issue. I will let you know if I find any issues tomorrow. Thanks for the ideas!:bigthumbsup
I checked over all the wiring and they were ok. I did notice corrosion build up on the positive terminal and it looks like someone may have scrapped the metal out of the positive cable. I cleaned all of my terminals and connections. I will run it and see if the issue goes away tomorrow.
I just tried the car and the battery was drawn down enough to have the starter try to turn but could not get it started. The starter stopped and the solenoid started clicking. I have a battery charger on it now and I am going to see if that will help.
The battery was just low enought to not turn the car over. I let the charger sit on the battery for about 30 min and it fired right up. I will probably try a new battery this evening.
More than likely your problem is with the Shaker 500 stereo. You did state that you pulled radio fuse and it helped. If you search these forums and the web you'll see all kinds of problems. We had 05 GT with Shaker 1000 and we had battery problems to. There is a relay internal in radio that doesn't turn all the way off and allows the amps to stay on and drain the battery. Most people say to turn radio off before turning car off. Others say eject all CD's (not sure why?) then turn off radio, then car.

As far as your battery posts... Go to autoparts store and get small packet of dielectric grease for batteries. After you clean them you can coat both battery and cable terminals. This will help with corrision.

You can check to make sure the alternator is charging by using a multimeter as the car is idling you can check voltage at battery terminals. It should be 13v or higher.
I just tested it with my multimeter and it was reading 12.5v as soon as I disconnected it from the charger and it eventually went down to 11.5v after about 5 min. of sitting out of the car charged. When the car was idling it was reading 12.5v and would not go move no matter what I had on. I am going to have the alternator tested tomorrow to see if it is putting anything out.

The voltage would drop down below 12v whenever the AC kicked on but it when right back up after the initial engagement. Other than that I did not see any fluctuations in the voltage.

The battery also has a built in hydrometer. It has a green and red ball in it. The indicator is currently yellow.
I tested the battery again and it was drawing down past 12.6v and leveling out at 11.5. I took it to the nearest dealership and asked them about replacing my battery. They told me that they would have to test it and see if it was the battery. I called up the dealership that replaced the battery when I bought it and they told me that the warranty would not be under me because the dealership put the battery in to pass inspections and that I would have to pay full price for the new battery (It was only 14 months old!!!!!) The battery failed the tests and would not even hold a charge long enough to start it back up after sitting for 5 min.

I paid the dealer for the tests and told them to give it back to me running. I went to the nearest parts store and changed the battery in the parking lot and it is working great now.:laughlitt

I have learned that fine print will always come back to bite you on warranties...oh well, at least I won't have any more junk motorcraft batteries in my car ever again! :nono:
See less See more
Battery should read at least 13.6 while the car is running. A 12 v batterry is dead at 12 volts. If the problem returns, the early shaker units were revised due to draining the battery. My 08 sits for weeks at a time and has no problem and I never turn the radio off.
Battery should read at least 13.6 while the car is running. A 12 v batterry is dead at 12 volts. If the problem returns, the early shaker units were revised due to draining the battery. My 08 sits for weeks at a time and has no problem and I never turn the radio off.
lol @ a 12volt battery is dead at 12volts. You can't be serious and still think you're right? Trust me, nothing could be farther than the truth. Anything under 11.3 and it's "dead" (and even then that may not be true) - 11.5, even 9 volts it will still start the car if the battery is good. It's the amps that starts it not the voltage reading. (Surrounded by military mechanics and I also know myself from experience.) Just like you can have 13volts battery reading and it wouldn't jumpstart a pissants motorcycle.
I've had your problem and the same non-existant warranty on the Motorcraft battery wasn't worth the paper they wrote it on. Believe it or not, your car is designed to "go to sleep", just like your computer. If you have anything plugged into your power points or cigarette lighter socket (other than the lighter unit), then your car detects this power drain and remains active pulling a lot more juice than when it sleeps. I started unplugging my power points and have no more problems. This is the info I got at the dealership and it appears to work for me. I had a radar detector and GPS and MP3 player all plugged into 2 power points and it was always going dead. It finally ruined the battery which I replaced and no more problems.
Oops, and yes, the alternator should be pumping 13.6 to 14.3 volts to your battery.:bigthumbsup
1 - 13 of 13 Posts
This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.