Hey guys looking for a bit of help on a certain issue.

I'll try to provide as much info as possible. First my vehicle specs. 2005 V6 5-Speed Legend Lime Mustang. at about 95k miles. I've owned the car since 2010 and have done most of my own maintenance.

I've noticed every once in a while It would take an extra second or two to start my car when turning over the past 6 months. No big deal. The battery was getting a bit old and I figured it was getting low.

About two weeks ago My belts started squealing bad, so I changed out my Serp Belt, A new OE Tension-er and a Idler pulley. The squeak went away. The next morning I went out and my battery was dead.

I figured it was time for a new battery since mine was about 6 years old and bought a new battery from AAP (Premium Gold). I installed the new battery and everything was fine for a few days.

While out driving that weekend, while at a stop I noticed the battery light had come on. Its the first time i have ever seen the light on this vehicle.

I took the battery out and brought it back to have it tested and it tested good and they re charged it to 100%

I figured that creeping up on 100k Miles the alternator likely went, So I swapped out a new OEM ford one and everything was good for about a week.

I got in my car today and as soon as I started my car the battery light is back on.

I did notice before some corrosion on the negative terminal, but I cleaned it thoroughly when I put in the new battery.

So to sum it up, Brand new Battery Brand New OEM Alternator and the Light has come back on.

Any tips would be greatly appriciated!

 

Call your local auto parts stores and see if they can do a charging system 'load test'. Then drive your Mustang to them. Some of these places have the machine but the guy using it doesn't know what they are doing or don't know how to properly use the machine. They will do it for free

 

corroded battery cables or grounds could cause enough resistance in the electrical system to reduce the actual voltage supplied by the alternator to the battery.

 

When you changed the alternator, did the squealing go away?
Recently had the same symptoms on a '07; it was the alternator. No more noise, no more battery/charging light on.

You might have gotten a bad alternator, or the fusable link in the cable may be blown. Check at the battery for voltage when running; it should be around 14v. If it's only 12v, the alternator is not charging or the alternator-cable portion of the battery cable harness has an issue (fusable link). I have a couple extra harnesses, if that ends up being your issue. Otherwise, make sure the alternator is indeed working right.