Car Won't Start: Battery, Starter Motor or Alternator?
Written by Petro Olekhnovych, mobile mechanic in Aylesham, Kent
If your car won’t start, the sound it makes is the best clue. Rapid clicking usually points to a flat battery, a single loud click with a charged battery points to the starter motor, and repeated flat batteries can mean the alternator is not charging. If the engine turns over but never fires, the problem is more often fuel, not electrics.
According to the RAC, a flat battery is the most common reason a car won’t start. But it is not the only one, and replacing a battery will not fix a starter or alternator fault. Here is how to narrow it down.
Listen first: what happens when you turn the key?
Rapid clicking, engine does not turn
The AA says a rapid clicking sound when you turn the key often means the battery. A failing alternator can also cause this, because it leaves the battery low.
One loud click, then nothing
A single loud click is usually a starter motor or starter relay problem, according to the AA. A bad earth connection can also cause it. The RAC says clicking with a charged battery is a typical symptom of a faulty starter or a wiring fault, which needs inspection and diagnosis.
Dashboard lights come on, but no sound at all
The AA lists several possible causes here: the ignition switch, a blown fuse, the starter solenoid or another electrical fault.
Engine turns over but will not fire
If the engine cranks normally but does not start, the AA says this is often a fuel problem. Causes include an empty tank, a flooded engine, a blocked fuel filter or a faulty fuel pump. A very fast cranking sound and a strong smell of petrol can point to flooding.
Engine starts, then cuts out
The AA links this to fuel injection or carburettor problems, flooding, or an immobiliser fault.
Battery, starter motor or alternator: how to tell
Flat or worn battery. Common causes are lights or other electrics left on, an electrical drain, long periods without driving, or a battery that no longer holds charge. The AA notes battery problems are particularly likely in cold weather. A jump start may get you going, but the battery may still need replacing.
Starter motor. The starter is the electric motor that turns the engine when you turn the key or press the start button. Autotrader says that if the lights come on and you hear a click with a fully charged battery, the starter is the likely culprit.
Alternator. The alternator keeps the battery charged while the engine runs. The RAC lists these signs of a failing alternator:
- a battery-shaped warning light on the dashboard while driving
- headlights or interior lights that are dim or flicker
- electrical items like windows or the radio playing up
- frequent flat batteries or difficulty starting
- a grinding noise from the engine, or a smell of burning rubber
If your battery keeps going flat even after a long drive, the alternator or charging system is worth checking. Our guide to the battery warning light explains what that light means when it comes on while driving.
Warning light on? We come to you.
Send a photo of the dashboard and your reg. We will tell you if it looks safe to drive and what it needs.
WhatsApp for a free quote Call 07563 350335
Labour £30 to £50 per hour depending on the job. Send your reg number and we will reply with a price before any work starts.
Other common reasons a car won’t start
Immobiliser or key fob. If the immobiliser does not recognise your key, the engine will not start. A flashing key symbol on the dash is a clue. The AA and RAC both suggest replacing the fob battery, holding the fob against the start button, or trying your spare key.
Steering lock. If the key will not turn at all, Autotrader says the steering lock may be jammed, often because a wheel is against a kerb. Gently turn the steering wheel from side to side while turning the key.
Fuel. Running out of fuel is a simple but common cause. If you have put in the wrong fuel, do not try to start the car. Autotrader says the fuel system needs draining, so call for roadside help.
Diesel in cold weather. If you drive a diesel and the glow plug light is flashing, see our post on glow plug light flashing.
What to try before you call for help
- Check the obvious: enough fuel, and lights or other electrics not left on.
- Try your spare key if you suspect the fob or immobiliser.
- Do not keep cranking. The RAC says not to try for more than a few seconds at a time, as you risk flattening the battery or damaging the starter motor.
- If the battery is flat, a jump start from a car with a fully charged battery may work. The RAC advises driving for at least 30 minutes afterwards so the battery can recharge.
- If it will not jump start, or keeps going flat, get the fault diagnosed rather than just fitting a new battery.
If a warning light comes on while you are driving, check our guide to dashboard warning lights to see whether you need to stop.
How we can help
When your car won’t start, getting it to a garage is the hard part. As a mobile mechanic based in Aylesham, we come to your home or workplace across Canterbury, Dover, Deal, Sandwich, Folkestone and nearby villages.
We can come out and diagnose the cause, whether it points to the battery, starter motor, alternator, wiring or fuel supply, then tell you what it needs. If the cause is a blocked fuel filter, we can replace it on the spot, for petrol and diesel cars.
Labour is £30-£50 per hour depending on the job and its difficulty, and parts are extra. We agree the price with you on WhatsApp before any work starts. If cold mornings are on the way, our winter car checklist is worth a read too.
Frequently asked questions
Why does my car click but not start?
Rapid clicking usually means a flat or weak battery. A single loud click with a charged battery usually points to the starter motor, starter relay or a wiring fault.
Can a bad alternator stop a car from starting?
Yes. The RAC says an alternator fault will prevent the car from starting correctly, because the battery is not being recharged.
How long should I drive after a jump start?
The RAC advises at least 30 minutes so the battery can recharge. A dedicated battery charger gives a fuller charge.
My lights work, so why won’t the car start?
With lights working but no start, the AA and Autotrader point to the starter motor, solenoid, ignition switch, fuses or wiring.
Need help? Send a WhatsApp to 07563 350335 with your car’s make and model and we’ll come to you.
Warning light on? We come to you.
Message us on WhatsApp with your reg and postcode for a price before any work starts.
WhatsApp for a free quote Call 07563 350335
Labour £30 to £50 per hour depending on the job. Send your reg number and we will reply with a price before any work starts.
