Quick answer
If the car will not start but runs fine after a jump start, the battery is the more likely problem. If the car starts but the battery warning light comes on, the lights dim while driving or the car dies soon after a jump start, the alternator is the more likely cause.
The two are linked: a failing alternator will not recharge the battery, and a weak battery can strain the charging system, so a proper test is the only way to be sure.
Step-by-step guidance
- Note the symptoms: slow cranking, clicking, a warning light on the dashboard, dimming lights or electrical faults while driving.
- Check the battery terminals for corrosion or loose connections.
- If you have a multimeter, measure battery voltage with the engine off and again with it running. A healthy charging system usually shows a higher reading when the engine is running.
- Have the battery and charging system tested by an auto electrician or battery centre.
- Replace only the part the test shows is faulty, and ask for the test result.
What to check
- Battery age and whether it has been flat repeatedly
- The battery warning light on the dashboard
- Condition of the drive belt that turns the alternator
- Whether the tester checked both the battery and the charging output
Common mistakes to avoid
- Replacing the battery when the alternator is the real fault
- Driving far with the battery warning light on
- Ignoring corroded or loose terminals
- Leaving accessories plugged in and draining the battery
Related nearby services
NearMe lists 34 auto electricians across South Africa, with the most in Western Cape (8), Gauteng (8) and Mpumalanga (4). 100% include a phone number, so you can check before you go.
Find auto electricians near you
This guide gives general information only. Rules, fees and requirements can change, so confirm details with the provider or the relevant authority. NearMe is an independent directory, not the provider.
Frequently asked questions
How long does a car battery usually last?
Typically a few years, commonly around three to five, depending on climate, driving habits and the battery type.
Can a bad alternator drain a new battery?
Yes. If the alternator is not charging, the car runs off the battery until it goes flat.
What does the battery light on the dashboard mean?
It usually means the charging system is not working properly, which often points to the alternator or its belt.