Q: Car won't charge after replacing battery and alternator

From the looks of it, you have done a lot of work on your Mustang. I can understand how frustrating it must be to get this far but still be experiencing problems with charging. The first question I would ask is if this previous work was performed all at once or gradually over some time, such as weeks or months. Many people will say that a part on their car is brand new, only to discover that the battery is a year old. It’s possible that the battery or alternator may have failed again but on different times.

Now, let us say there is a definite new battery and alternator in the Mustang and all known grounds are good. Yet for some reason your Mustang is still not charging. From there, we can move toward the inspection that there is likely to be a wiring issue between the alternator and battery. With new parts, this is probably really frustrating for you. I believe it is best to enlist the help of a certified mechanic to ensure a proper diagnosis and repair of your battery and alternator.