How To Diagnose Bad Alternator. See all that black dust around that area? In order to diagnose a bad alternator, you will need a multimeter.
A bad alternator leads the vehicle to use up all of the battery’s capacity. Be sure to keep an eye on the gauge to see if it decreases sin voltage or amperage. If you find code p0562, you very likely have a failing alternator (note that codes may vary by vehicle make/model/year).
If the headlights flicker, dim or get brighter when the accelerator is. Bad alternator clutch pulley symptoms. If you have an alternator light in your dashboard, it should light up every time you start the engine.
When the 'check engine' light turns on, connect the code reader to the diagnostic port. Because an alternator that is charging the battery will produce 13 (up to 14.5) volts with the headlights on or off and/or with everything on (so if the test above gave you steady, and i emphasize steady,13 and up to 14.5 volts with everything on, then your alternator is not bad). If the p0562 code appears, it is very likely that the alternator is in bad condition (it should be noted that the codes may vary depending on the make / model / year of the vehicle).
If you notice too much noise in the engine that lasts for 1 to 5 seconds after shutting it down then it is most probably the alternator clutch pulley that is at fault. Probably dead regulator or broken wiring or failed alt switch or breaker. Alternator fuse (if there's one) the lead between the alternator and the battery;
When the alternator starts to fail, it will light up a “check engine”, “alt” or a battery icon indicator. And whether you're driving a ford, a chrysler or a dodge or a plymouth, a nissan, a mitsubishi, a. The truth is, there’s no way to know how long it will last.
A loose or bad belt can cause the alternator to run incorrectly, so a quick inspection of the belt can diagnose the problem. Voltage there, and it won't produce? Other problems can also cause a car to not start.