Diagnosis · 2 min read

Battery or alternator? How to tell why your car won’t start

A plain checklist to tell a dead battery from a failing alternator or starter, and what to do next.

A car that will not start is usually a battery problem, but not always. A few quick observations will tell you whether you need a new battery, a jump or a mechanic.

Signs it is the battery

  • The engine cranks slowly or makes a rapid clicking sound, then nothing.
  • Dash lights are dim or flicker when you turn the key or press start.
  • The car starts fine after a jump, then will not start again after sitting.
  • The battery is more than three years old, or the case is swollen.

Signs it may be the alternator

  • The car starts, then dies while driving.
  • Headlights dim and brighten with engine speed while you drive.
  • The battery warning light comes on while the engine is running.
  • A new battery goes flat again within days.

Signs it may be the starter

  • Dash lights are bright and normal, but turning the key gives a single click or no sound.
  • You hear grinding or whirring without the engine turning over.

What to do next

If it looks like the battery, we can bring and install a replacement where the car is. Tell us about the symptoms when you book. If what you describe sounds like an alternator or starter problem, we will tell you before sending anyone, so you do not pay for a battery you do not need.

Book a battery replacement or call us to talk it through.