Car wont start is the search people make from the driveway, phone in one hand, keys in the other, already late. Before you call anyone, there are checks that take two minutes and will tell you which of three things you are dealing with. Battery, alternator or starter motor. Getting that right is the difference between a cheap morning and an expensive one.
Car Wont Start: The Short Version
If your car wont start, what it does when you turn the key tells you almost everything. A slow crank points at the battery, a single loud click with bright lights points at the starter, and a car that started fine then died while driving points at the alternator.
Before calling anyone, check the headlights, the battery terminals, that the car is properly in Park or Neutral, and the key fob battery. A loose or corroded terminal behaves exactly like a dead battery and costs nothing to fix.
A car wont start situation that keeps repeating, where every new battery goes flat, is a parasitic drain rather than a battery problem.
Start With What Actually Happens
Turn the key or press the button and pay attention to exactly what the car does. This one observation narrows it further than anything else.
| What happens | Most likely cause |
|---|---|
| Engine turns over slowly, then catches | Battery low but not dead |
| Rapid clicking, dash lights dim right down | Flat battery, or a corroded or loose terminal |
| One loud single click, lights stay bright | Starter motor or starter solenoid |
| Nothing at all, no lights, no dash | Completely flat battery, or a disconnected terminal |
| Cranks normally but will not fire | Fuel, spark or timing. Not the battery |
| Started fine, then died while driving. Battery light on | Alternator, not the battery |
| Dash lights come on then everything cuts when you turn the key | Battery cannot hold under load |
The Two Minute Checks Before You Call Anyone
- Turn the headlights on. Bright and steady means you have battery voltage. Dim, yellow or nothing means the battery or a connection.
- Look at the battery terminals. White or blue crust, or a terminal you can wiggle by hand, is a genuine cause of a no-start and it is free to fix. Tighten or clean and try again.
- Check the car is properly in Park or Neutral. Automatics will refuse to crank if the selector is not registering. Try starting in Neutral instead of Park.
- Press the brake pedal firmly on push-button cars. A weak press is a common reason nothing happens.
- Check the immobiliser and key. A flat key fob battery stops some cars starting. Hold the fob against the start button if your car supports it.
- Listen with the window down while someone turns the key. Single click, rapid clicks or silence are three different answers.
Those six checks resolve a surprising number of no-starts before anyone touches a spanner. The terminal one in particular: a connection that looks attached and is not making proper contact behaves exactly like a dead battery.
If It Is the Battery
The most common answer, and the one with the clearest tells. Slow cranking that got worse over weeks, headlights that dim at idle, a car that needed a jump before, electrical oddities like the clock resetting.
A jump start will get you going. What matters is what you do next. If the battery is over three years old and it has now let you down, it will let you down again. If it is nearly new, the battery is a symptom rather than the cause and something else is draining or not charging it.
Our car battery replacement guide covers the costs, how long batteries last in Australian heat, and why start-stop cars need a specific type.
Jump Starting Without Damaging Anything
- Match the voltage and connect positive to positive first, then the donor negative to an unpainted metal point on the flat car rather than its negative terminal.
- Let the donor car run for a few minutes before attempting to start.
- Do not rev the donor car hard. Modern electronics do not appreciate it.
- Once running, drive for at least twenty minutes. Idling in the driveway puts very little back.
- If it will not start again the next morning, the battery is not holding charge. That is your answer.
If It Is the Alternator
The alternator recharges the battery and runs the car while the engine is going. When it fails, the car runs off stored charge until there is none left.
The pattern is distinctive: the car started fine, then died while driving, often with the battery warning light on and the headlights fading. Or you jump it, it runs for twenty minutes and dies again.
Two things worth knowing. First, the battery warning light does not mean the battery is flat. It means the charging system is not keeping up, which usually points at the alternator or its drive belt. Second, a failing alternator will destroy a brand new battery, which is why fitting a battery without testing the charging system is money thrown away.
Sometimes it is not the alternator itself but the belt that drives it. A belt that has snapped or is slipping will also stop the water pump and power steering on many cars, so a sudden loss of steering assistance alongside a charging fault is a strong hint.
If It Is the Starter Motor
The signature is a single loud click with the dash lights staying bright. There is plenty of power available, and the starter is not doing its job.
Sometimes it is the solenoid rather than the motor. Sometimes it is a worn contact that works intermittently, which is why some cars start every time for a week and then refuse once. Intermittent no-starts with strong lights are very often a starter, and they are frustrating precisely because the car behaves perfectly whenever you take it anywhere.
The old trick of tapping the starter with a hammer sometimes works and tells you something useful: if it starts after a tap, the starter is on its way out.
If It Cranks Normally but Will Not Fire
This one is different from the other three. The battery, alternator and starter are all doing their jobs. The engine is turning and not catching, which means fuel, spark or timing.
- Fuel. Genuinely empty tanks are more common than people admit, and a failing fuel pump usually gives a few weeks of hard starting first.
- Spark. Worn plugs or a failed coil. Often accompanied by rough running before it stopped entirely.
- Immobiliser. The car cranks but the engine management will not allow fuel or spark. Usually a key or fob issue.
- Timing. A snapped timing belt will crank freely with no compression at all. AutoGuru covers what timing belt replacement involves, and the job costs a great deal less than the engine damage a broken belt causes. If your car has a belt and it was overdue, this is the possibility to take seriously. Our timing belt guide covers why.
A car that cranks and will not start needs diagnosis rather than parts. Fault codes and a few live readings will normally identify it quickly.
If It Keeps Happening
A car that goes flat every few days, or every time it sits for a week, has a parasitic drain. Something is drawing current when the car should be asleep.
Common culprits are aftermarket alarms and dash cameras wired to a permanent live, a boot or glovebox light that never switches off, a failing door latch switch that keeps a module awake, and a diode inside a failing alternator.
This is worth testing properly rather than replacing batteries repeatedly. If every new battery goes flat, the battery was never the problem.
Starting and Charging Diagnosis at Hot Tyres Riverwood
We test batteries under cranking load, check alternator output across the rev range, test starter motors and measure parasitic drain, at 74 Belmore Rd North, Riverwood. We also carry out battery, alternator and starter motor replacement, so the same visit finds the fault and fixes it.
If your car will not start, tell us what it did. Slow crank, single click, rapid clicking or complete silence. That one detail usually points straight at the answer.
Open Monday to Friday 8:00am to 5:00pm, Saturday 8:00am to 3:00pm. Phone (02) 9533 6138.
The Cold Morning Version: What to Do in Order
If you are standing next to the car right now, work through this in sequence rather than jumping to a conclusion.
Minute one. Headlights on, look at them. Bright and steady is one world, dim or dead is another. Then wiggle the battery terminals by hand. If either moves, tighten it and try again before doing anything else.
Minute two. Try starting in Neutral rather than Park. On push-button cars, press the brake hard and hold the fob against the start button. Listen carefully with the window down while you do it.
Minute three. Decide what you heard. Nothing, a single click, rapid clicking, a slow crank or a normal crank that will not fire. Those are five different problems and the answer determines who you call.
If you get it going. Drive for at least twenty minutes before switching off. A short trip after a jump start puts back almost nothing, and you will be in the same position tomorrow.
If you do not. Note exactly what it did before you ring anyone. “Single click, lights stayed bright” gets you a far more useful answer than “it will not start”.
Why This Happens in Summer, Not Winter
Most people assume cold kills batteries. In Australia it is the opposite, and the timing catches people out every year.
Heat is what degrades a battery. Sustained high temperatures accelerate the internal chemistry that wears the plates and evaporates electrolyte. A Sydney summer does more damage to a battery than a Sydney winter ever will.
What cold does is expose the damage. A cold engine is harder to turn and a cold battery delivers less current, so a battery weakened over summer finally fails on the first properly cold morning. The damage happened in February. The failure happens in June.
- If your battery is over three years old, test it before summer, not after.
- Park in shade where you can. Under-bonnet temperature is what does the damage.
- Short trips make it worse, because the battery never fully recovers what starting took out.
- A car that sits for weeks at a time is worse again, because modern cars draw current constantly even when off.
The practical takeaway: a battery that felt slightly slow in autumn is a battery that will fail, and replacing it on your terms is considerably cheaper than replacing it on a tow truck driver’s. Our car battery replacement guide covers what the different types cost.
Frequently Asked Questions
My car wont start but the lights work. What does that mean?
Bright lights with a single click usually points at the starter motor or solenoid. Bright lights with rapid clicking is more often a battery that cannot deliver cranking current, or a poor terminal connection.
Is it the battery or the alternator?
If the car starts after a jump and then dies while driving, it is the alternator. If it starts after a jump and runs fine but is flat again the next morning, it is the battery or a parasitic drain.
What does one loud click when I turn the key mean?
Usually the starter motor or its solenoid, provided the dash lights stay bright. It means power is reaching the starter and the starter is not engaging.
Why does my car crank but not start?
The battery, alternator and starter are working. That leaves fuel, spark, the immobiliser, or timing. A snapped timing belt will crank freely with no compression.
Can a bad battery terminal stop a car starting?
Yes, and it is one of the most commonly missed causes. A corroded or loose terminal behaves exactly like a dead battery and costs nothing to fix.
My car goes flat if it sits for a week. Why?
That is usually a parasitic drain, something drawing current while the car is off. Aftermarket alarms, dash cameras, a light that stays on or a failing alternator diode are common causes.
Will jump starting damage my car?
Not if it is done correctly. Connect positive to positive first, then the donor negative to an unpainted metal point on the flat car rather than its negative terminal, and drive for at least twenty minutes afterwards.
What should I do first if my car wont start?
Turn the headlights on and check the battery terminals. Bright lights with tight terminals rules out the two most common and cheapest causes in under a minute.
Why does my car only fail to start on cold mornings?
The damage is usually done in summer heat, and cold weather exposes it. A cold engine is harder to turn and a weakened battery cannot deliver the current, so the failure appears months after the cause.
How long should I drive after a jump start?
At least twenty minutes of actual driving. Idling in the driveway puts very little charge back and you will likely be flat again the next morning.
Should I replace the battery or test it first?
Test it. Fitting a battery to a car with a failing alternator or a parasitic drain wastes the money, because the new battery will go flat too.
Can a key fob battery stop my car starting?
On some cars, yes. If the fob is not being detected the car will not authorise a start. Holding the fob against the start button is a common workaround worth trying.