Q: How to know if the alternator is bad
Car won't start consistently, but will start after jumps SOMETIMES.
But then, once it's jump started, driven a short distance, then tried to restart, it is dead.
My car has 100000 miles.
My car has an automatic transmission.
In order to know if the alternator is bad it will need to be tested using a volt and amp meter. Also the engine will need to be scanned to see if the computer is controlling the alternator charge output. I would recommend having a mechanic like one from YourMechanic come and test voltage and amperage output of the alternator to see if it stop charging or there is a computer and wiring problem.
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