Car dies when headlights are turned on

saturn
sl

#1

My friend says she needed a jump to get started yesterday and when she turned on the head lights, the whole car died. Unfortunately I wasn’t the one who jumped her so I’m not sure of any other details.



We’re thinking the battery might need to be replaced, is this an accurate assessment?


#2

The battery may or may not need to be replaced, but the alternator very likely is bad. Once the engine is running, the alternator should have been able to handle the extra load of the headlights.
Some of the auto stores will test both the battery and the alternator at no charge. Be aware that it is possible that some other electrical system fault is the issue and not the alternator. That would generally be loose or corroded wiring.


#3

It definitely sounds like the alternator needs replaced. If turning on the headlights overwhelms it and causes the car to die, the output is not enough to charge the battery. The battery may need to be replaced as well. To find out, you will have to charge it and load test it. If you don’t know how to do this properly, any decent mechanic should be able to help you.


#4

Thank you both, we’ll get it tested at an auto store before jumping on buying a battery.