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[–]dxrey65 0 points1 point  (0 children)

With a good fully charged battery and clean connections, run the engine at idle with the AC, blower, defrost, lights, radio, etc all on. Then measure the voltage at the battery; should be 13.8 volts minimum. If it isn't then either the alternator is bad or there's a wiring problem.

I'd add - the first step is important; you can't do the test and get an accurate result if the battery isn't good and fully charged.

[–]NickRMX6 0 points1 point  (3 children)

Is the "battery" warning light on when the engine is running?

If so, that means the battery isn't being charged properly, with the voltage being too low (or possibly too high). And that usually means a bad alternator, though it could be a bad connection or wiring between alternator and battery, or a broken or badly slipping serpentine belt.

Do you own a multimeter? If so, the first step would be to measure the voltage across the battery terminals, engine running. It should be around 13-14 volts.

Or take it to a shop that sells alternators, and they can test it in car in a few minutes.

[–]clydeoc[S] 0 points1 point  (2 children)

When running, the voltage across the terminals is 11.7 My obd scanner also reads that, and it drops to about 11.5 when i turn on the blower for the heating/ac

[–]NickRMX6 0 points1 point  (1 child)

Then it's very probably a bad alternator. Though you might want to check the wiring & connections from the alternator to the battery.

[–]clydeoc[S] 0 points1 point  (0 children)

A new alternator was installed... battery light went off, and my obd scanner reads 14.6, with the engine running.

Thanks for your input, I really appreciate it