Car Won't Start: Is It the Battery or the Starter?
You turn the key and nothing happens, or the car makes a strange noise. The two most common causes are a weak battery and a faulty starter motor, and they can look similar. The sounds the car makes and what the lights do give you strong clues.
Short version: rapid clicking and dim lights usually mean a weak battery. A single loud click with bright lights points to the starter or its connections. A jump-start or a quick voltage check can tell you which.
Listen and look
| What happens | Likely cause |
|---|---|
| Rapid clicking, dim lights | Weak or flat battery |
| Engine turns over slowly, then stops | Weak battery |
| Nothing at all, no lights, no dashboard | Flat battery, or loose or corroded terminals |
| One loud click, lights stay bright | Starter or starter relay fault |
| Engine cranks at normal speed but will not start | Not the battery or starter. Look at fuel or ignition. |
| Starts with a jump but dies soon after | Alternator not charging |
Quick checks you can do
1. Test the lights
Switch on the headlights and then try to start the car. If the lights go very dim or go out, the battery is weak. If they stay bright but the engine does not turn, suspect the starter.
2. Check the terminals
Look at the battery posts. White, blue or green crust, or clamps that move when you twist them, can stop the starter getting enough current. Clean and tighten them. See how to clean battery terminal corrosion.
3. Check the voltage
With a multimeter across the battery terminals, a charged battery should read about 12.6 V. If it is below about 12 V, it is flat or failing. Watch the reading as someone tries to start the car. If it falls very low, the battery is weak. If it stays high but the car does not start, the starter is more likely. See how to test a car battery.
4. Try a jump-start
If the car starts at once with a jump, the battery was the problem, though it may be the charging system that let it go flat. If it makes the same single click even with good jump cables connected, the starter or its wiring is the likely cause. Follow the correct order. See how to jump-start a car safely.
5. Check the basics
- On an automatic, make sure the gear selector is in park or neutral.
- If your car has an immobiliser light flashing, the key may not be recognised.
- Check that the steering lock is not holding the key.
- Make sure there is fuel in the tank.
If the starter is the problem
A failing starter often gives warning signs first: slow or intermittent starting, grinding noises or a click without cranking. It may be the starter motor itself, the solenoid, a relay or a corroded cable. Do not hit components with tools to get the car started. Have a mechanic or auto electrician test it.
If the battery is the problem
- Recharge or jump-start the car and drive it for at least 20 to 30 minutes.
- Have the battery and the charging system tested.
- If it is worn out, replace it. See how to choose the right car battery and how to replace a car battery safely.
- If it keeps going flat, read why does my car battery keep dying?
Safety
- Never jump-start a battery that is cracked, leaking or swollen.
- Keep sparks and flames away from the battery.
- If you are unsure, call a mechanic rather than forcing the problem.