Stuck on the road? Get safe before you get it going
Hazard lights on, and get as far left as you can. On a motorway, AA New Zealand's advice is to stay in the car with seatbelts on, in the seats furthest from traffic, unless getting out feels safer; then leave on the side away from traffic and wait behind a barrier or well off the road. Ring *555 if the car is a hazard but nobody's hurt, and 111 if anyone is hurt or at risk.
What does the car do when you turn the key or press start?
| Most likely | First thing to try | |
|---|---|---|
| Nothing at all, dash dark | A flat battery or a loose terminal | A jump start or a battery test |
| Rapid clicking, dash dims | A battery too weak to turn the starter | A jump start, then find out why it went flat |
| One loud click, lights stay bright | The starter motor or its solenoid | A mechanic's test of the starter circuit |
| Slow, laboured cranking | A tired battery, worst on cold mornings | A battery and charging test |
| Cranks normally but won't fire | Fuel, ignition or the engine computer | Check the fuel, then a diagnosis |
| A hybrid that won't show READY | Can be the small 12-volt battery | A test of the 12-volt battery |
The battery seems fine, but the car still won't start
If the lights and radio are bright and the engine spins at its usual speed, the battery has done its part. The trouble is further along: the engine isn't getting fuel, a spark, or the right signal from its computer.
Check the obvious first. Is there fuel in the tank? Could it have had the wrong fuel at the last fill? AA New Zealand's advice there is to leave the ignition off altogether, because on many cars the pump in the tank starts running as soon as it's switched on.
A car that cranks but won't fire is a diagnosis job. AA New Zealand lists it among the warning signs of a failing engine computer, alongside the more everyday suspects a mechanic will check: the fuel pump, sensors and the immobiliser.
What to check, in this order
Gear selector and clutch
An automatic has to be in Park (or Neutral), and many manuals won't crank without the clutch pressed right down.
The key or fob
If the fob battery is low, the car may not recognise it. The owner's manual shows the backup way to start it.
The dash lights
Bright, dim or dark? Dim or dark sends you to the battery.
The battery terminals
Look, without touching, for crust or a loose clamp. The MTA lists corrosion around a terminal as a sign of a failing battery.
Then stop cranking
Cranking over and over flattens what's left in the battery and heats the starter. If it hasn't fired after a few short tries, ring for help.
Is a jump start safe?
Usually, done carefully and by the book. The owner's manual shows where the leads go, and some cars have jump points under the bonnet away from the battery. AA New Zealand warns that a jump pack connected the wrong way round can damage sensitive electronics.
Never jump a battery that's cracked, swollen or leaking. And a jump only gets you going: AA New Zealand says the alternator is there to keep a battery charged and run the car, not to revive a dead one, so plan on a proper charge or a test.
Hybrids and EVs: it's often the small battery
An Aqua, a Prius or a Leaf still carries a 12-volt battery alongside the big one. AA New Zealand says that if an EV won't start, that small battery may have gone flat, and a hybrid behaves the same way: the main battery can be full and the car still won't wake up.
The jump points and the order matter on these cars, and the manual's steps come first. A mechanic who does hybrid and EV work can test and replace the 12-volt battery where the car is.
What the mechanic will do
Test the battery under load and check the alternator's charging, then look at the starter circuit if the battery passes. Inside the starter, a solenoid pushes a small gear out to turn the engine's flywheel, so one click with no turn often means the solenoid or the motor. If it cranks and won't fire, they'll check fuel pressure, spark and the stored codes.
A mobile mechanic can do most of this where the car is sitting, which saves a tow when the fix turns out to be a battery or a starter connection.
What you can do, and what's the mechanic's job
You can
- Check the gear selector, the clutch and the key fob.
- Read the jump-start pages in the owner's manual before connecting anything.
- Note exactly what the car did: click, crank, silence, or start and stall.
Leave to the mechanic
- Battery load tests and charging checks.
- Starter motor and solenoid testing.
- Fuel, ignition and computer diagnosis on a car that cranks but won't fire.
If it were our car
If the clues point to the battery, we'd try one careful jump start, and if it fires, head for a battery and charging test rather than trusting a drive to fix it. If it cranks strongly and won't fire, we'd stop cranking and send it as a diagnosis job, with the sound it makes in the note.