Knowledge base · Symptom & cause
Car won't start: battery, alternator or starter?
You turn the key and what should happen doesn't. Before you think about a tow truck: the noise the car makes at that moment almost always tells you where the problem sits. Four scenarios.
Scenario 1 — Nothing at all, completely dead
No lights, no click, no display. This points to a flat or faulty battery, or a bad connection. Check that the battery terminals are clean and tight; green-white corrosion is a classic. If the interior light works but dies when you turn the key, the battery is flat rather than dead.
Scenario 2 — Rapid clicking
A rattling, rapid clicking almost always means: not enough voltage to turn the starter motor. So again the battery, or the connection to it. Jump leads usually help here — but if the car keeps going flat afterwards, the cause lies elsewhere: a battery at the end of its life, a parasitic drain, or an alternator that isn't charging.
Scenario 3 — One hard click, no cranking
One solid "clunk" and then silence, while the lights stay normal: voltage is arriving but the starter isn't turning. Often this is the starter motor itself or the solenoid on it. Jump leads will not solve this one.
Scenario 4 — It cranks but won't fire
Battery and starter are doing their job; the problem is fuel, ignition or signal. Think spark plugs or glow plugs, fuel pump, or a sensor the control unit uses to time injection. Here a diagnostic readout genuinely helps — see car diagnostics explained.
And the alternator?
The alternator charges the battery while you drive. If it isn't charging, the car still starts the first few times and then suddenly doesn't. Signs: the red battery light on while driving, lights dimming, or the car stalling on the road. A new battery won't fix that — it will be flat again within days.
Jump leads: brief but important
- Switch both cars off and never let the clamps touch each other.
- Positive to positive, negative from the donor car to an earth point on the receiving car, not to the negative terminal.
- After starting, let the car run or drive for at least half an hour.
- If the problem keeps returning, have the battery and charging system measured rather than jump-starting every morning.
Winter exposes weak batteries
Cold reduces battery capacity and thickens the oil, so more starting power is needed. A battery that just about copes in October gives up in January. During a check on the lift we measure battery condition and charging voltage — a few minutes' test that saves you a morning without a car.
Want the cause found instead of guessed? That is brand-specific diagnostics in Tilburg.