movielover40

Most Battery Wholesale shops will test your charging system free with battery installed in car.

rayfromtexas

I am having the same problem on my 07 GT. It has worked fine for years (purchased new) and only recently has it been acting up. Battery replaced Feb 2015, alternator replaced September 2015 (so both fairly new). Belt is less than 2 years old, all pulleys are good. Checked all connections for security, corrosion, etc. Occasionally the CHECK CHARGING SYSTEM warning comes on and the battery light comes on, the battery indicator needle will spike to high, lights will dim/flicker, the ABS and traction control warning lights will come on then go out. Nobody seems to have a definitive answer...I see things like "Ford did not engineer the ground wires correctly, you need to add more grounds!" which is bs. I really don't want to take it to a dealer and spend $90/hr to have them try and sell me a new alternator or battery or tell me they can't find anything wrong. There MUST be someone on all the Mustang forums that really knows what the problem is!

SCCAGT

Just because a part is new, does not mean it is good. May have to time an alternator test at the same time the charging light comes on.

Simon1

I'm on my fourth alternator. I have no idea why they are sick pieces of ****, but they are.

For our cars, take the alternator off and have it bench tested. Testing white on the car does not seem accurate.

When you get another alternator, get one with a lifetime warranty and learn how to change it.

Chromeshadow

Most alternators are great and need to pass some extremely tough tests before they can be sold. Your car may have something about it that is damaging the alternator. It could be as simple as an intermittent ground cable from the engine to the frame. I would start by removing, inspecting and cleaning each high current cable in your car, including every ground strap. Any cable that looks at all worn, or looks like it may have been repaired at one time-I'd replace. Any bolts or fasteners that look at all corroded- I'd replace. Clean the area the ground straps bolt to and cover them with dielectric grease. Make sure the battery is properly secured and the + terminal does not hit the hood or any metallic areas.