Q: Battery good, alternator good, brand new alternator cable, still not charging.

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I need help finding out what could be wrong with my charging system. One day my 2003 Expedition didn't start, got a jump start and took it to auto zone to check. Battery voltage was too low to test, so I took battery out and left it out overnight, next morning picked it up, they said battery was good and held charge. Put battery back in and took it for testing, their test said the voltage regulator was bad, so bought a new alternator, installed it, same thing, not charging. Took old alternator back so they could run a bench test, old alternator came back good. So I just recently replaced the alternator cable thinking maybe it was the cable... nothing, still not getting a charge. My multimeter is only reading the current volts on the battery while engine is running, reading 12.4 volts and slowly draining. I can't think of anything else. As far as I know, I don't know of any fuses or relays assigned to the charging system. Please help. Thank you.

My car has 190000 miles.
My car has an automatic transmission.

Hi There, The first diagnosis of the bad voltage regulator is likely the cause of your charging system not properly charging the battery. When the voltage regulator is not working properly, this may result in the alternator allowing too much power to be delivered to the battery resulting in damaging wires and prematurely sometimes destroying the battery. In other cases it may result in the alternator not supplying enough power to the battery, resulting in undercharging the battery or not charging it at all. In some cases when a battery is too weak or damaged, it may no longer hold a charge for any length of time, in which case the alternator may be doing its job, but the battery is just simply too weak to hold a charge. In either case, I would recommend having an expert from YourMechanic come to your location to diagnose your vehicle’s charging system.

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