alternator or battery

[lerfin]

how do i know if my car is not starting it is the alternator or the battery

thanks

[rahulkh]

Jump start and let it idle for 10 mins or 20 mins, then switch off and start.

If it starts it was battery and now its fine, dont worry do same test after 2 hrs.

If it doesnt then that means battery is dead and beyond recharging and car was running on alternator only.

If alternator is dead, then in first instance car will not run for 20 mins and switch off of its own as soon as battery power run out.