Check charging system

[napathia]

Need HELP !!!!!


2011 Mustang GT

I have been getting a check charging system light on, also batt. Will not stay charged. I had the batt.checked and also the alternater ,both are good .

Never had this happen until I went to pick it up from being tuned. Tuner checked and said it was the alternator. I drove the car 3 hours to the tuner with no issue. But when I picked it up, light was on but went off. Came back on while driving home and continues to stay on while draining the battery completely down. Took alternator off, had it checked and all was good. Had battery checked, also good.

Stuck and need some advice.

 

[2014_GT]

Been through this before but with a F150 that I had. Turned out it was the battery even though it "passed" the test.

 

[5lho]

Load test the battery....Have someone crank the car with the ign system disabled and have a voltmeter across the batt terminals. If it drops to 11.8 or less, or won't recover to a little over 12 volts, junk the battery and replace it.

 

[JEWC_Motorsports]

Load testing is the only correct way to test a battery. The bullshit testers only check to make sure a few of the cells are good.

 

[napathia]

Although battery and alternator both tested good. Still had issues. Decided to start with a new battery since it is almost 4 1/2 years old. I don't drive it much so thought that might be the culprit. After replacing battery I was still having issues. Replaced alternator today and everything seems to be in working order again. Old alternator was tested by reputable electric shop and appeared to be good but evidently not. Thanks for your input.