Hi guys, I'm new here so if this issue has been posted before I'm sorry but I'm at my wit's end with this damn problem. I have a 2007 Mustang GT Convertible and a couple months ago I started to review the check Charging System light. It would come on while I was driving for a few minutes then turn off. Sometimes twice a ride but always at least once. I never had any issues with stalling out or a dead battery but I was worried because I had a feeling it would fail at the worst possible time. So I started digging and found horror stories of people going through five and six batteries and alternators a year. On one thread I found a guy who said it was a grounding issue and that I should install a ground from the negative terminal to the bolt that holds the alternator to the bracket. Many people said this worked for them, but when I did it I saw no change. Since my alternator was still stock and my battery is only a couple months old I said ok I'll try changing the alternator, at this point I had around 80,000 miles on it (the problem started around 74,000). So I changed it out, along with a new belt and now the check Charging System comes on a minute after I start it up and doesn't go off. I checked the battery and alternator with a voltmeter and they are both within range. The battery is 12.88 with the car off, and when it's running the alternator is between 13.8 and 14.3. I just took it all apart today to check the connections and wires thinking maybe I missed something but they all look good. I have no idea what else to do. Does anyone have any suggestions?

 

Where did you get the alternator from? The 05-09 Mustangs have notoriously fickle rectifiers in their alternators. A lot of cheap rebuilt and aftermarket remaned alternators are bad out of the box. Voltage may be fine but the sine wave the alternator is throwing out could be very noisy and thus throwing the light.

Either take it back to where you got it and exchange it or take it to a shop and have them look at the sine wave to confirm it first.

 

It is a Wilson professional series alternator. Do you have any brands that you would suggest? I've heard a lot of people use the 2010 alternators because they fixed the issue that year.

 

Never heard of them. https://www.paperformance.com/ is a popular one on the forum but very expensive.

Personally I used this one and it's been great for going on 18 months here in AZ.

I've heard about the 2010 swap.Again, I would advise you to verify the problem before throwing parts at it. I THINK it's a bad alternator but until you have proof, that's just a guess.