No shop seems to know why my battery light is on, so I am on here to reach out for more ideas to maybe fix this problem on my 2000 Mustang GT.
1. Was leaking antifreeze, so i got a new radiator, hoses and then a coolant flush.
2. was called by the shop telling me battery light came on. (no prior issue)
3. testing was done and nothing could be found, so it was recommended a replacement alternator.
4. manufactured aftermarket alternator was put in. Battery light still on.
5. Drove about a week, then on the way to work, had to pull over due to a high voltage reading on my dash battery gauge..wayyy past the H.
6. Drove it back to shop and was recommended my Mustang need a Motorcraft alternator.
7. Motorcraft alternator (manufactured) was put in, battery light went off.
8. 24 hours later, driving home from work, the battery light is back on.
9. Coolant light came on over the weekend and I put a little more antifreeze in. Coolant light went off but BATTERY LIGHT STILL ON!!
SO FRUSTRATING!
Does anyone else know what the issue is and how to get that light off??
Thanks so much!

 

Also the battery is good.

 

Welcome to the forum, glad to have you.

Just a little advice for next time, on these types of technical questions, start a thread in the appropriate Tech section, you'll get alot more responses sooner because of the number of people in that part of the forum.

As for your charging issue, the battery light comes on when it sees a voltage less than 12volts. I'm not familiar with the newer Mustangs , so that's a ballpark figure, but close. I'm surprised they put in a new alternator because they are very easy to test if they ARE bad . But to have 2 alternators go bad makes me wonder if it's something else.

With all the coolant issues lately, it could be possible that some was spilled or splashed onto the serpentine belt causing a slip on the alternator pulley. Usually you'll hear a slight squeal when this happens, but not always.

Just a thought,. Good luck

 

I spent a lot of years in the repair business, my favourite thing to hate is techs that don't trouble shoot, they just replace stuff until things work. Find another shop, don't take anything back to this shop. Take your car to Autozone they will test the alternator for free. Btw, always clean the battery posts and the clamps on the battery cables with a battery post brush. They may look clean but they get a layer of corrosion on them and should be cleaned each time you remove and reattach them! I'd check the engine ground strap (or just replace it) make sure you sand off the contact area-it should be shiny- not rust at all.