Alternator and charging system
The alternator generates the electricity the car uses while running and keeps the battery charged. When it fails, the car draws down the battery until there is nothing left — which is why an alternator failure often looks like a battery problem at first.
That is also why we test the charging system before replacing anything. A car that keeps flattening its battery might need an alternator, a battery, a belt, or just a clean connection.
Signs of a charging fault
- Battery warning light on while driving
- Headlights dimming and brightening with engine speed
- A repeatedly flat battery, especially a fairly new one
- A whining or grinding noise that changes with revs
- A burning-rubber smell from a slipping belt
- The car dies shortly after a jump start
What we check
- Charging voltage at idle and under load
- Alternator output against specification
- Drive belt condition and tension
- Battery condition — the two faults look alike
- Wiring, grounds and connections at both ends
We tell you what we found and what it costs before we do the work. Nothing happens that you did not agree to.
Frequently asked questions
Is it the battery or the alternator?
They present almost identically. Testing the charging voltage with the engine running separates them in minutes — which is why we test rather than replace and hope.
Can I drive with the battery light on?
Only far enough to get somewhere safe. That light means the car is running on stored battery power, and when it runs out the engine stops — possibly in traffic.