Car only runs if battery is fully charged for about 30 minutes. If u start the car then unhook the battery it doesn't run off the alternator it dies instantly. So of course every shop said oh replace your Alt which I did twice n still same thing. If you take the alternator off and test it it works fine as well as if you charge the battery it gets a full charge but if you test the alternator while on the car it reads nothing at all as if it's bad. I can't keep paying shops to change or test telling me it's a bad ALT when it's not that are the battery..Any Help on the subject?
My car has 144000 miles.
My car has an automatic transmission.
Hello. If the alternator is testing good then you probably have a failure in the control circuit for the alternator. This can be a fuse, wiring or it can be the computer. I usually need to test the circuit with a voltage meter to find out where the issue is. If you want to have this done, consider YourMechanic, as a certified mechanic can come to you to [see why the alternator is not charging] https://www.yourmechanic.com/services/battery-will-not-hold-a-charge-inspection
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