Alternator

What it does

Charges the battery and powers the electrics while the engine runs.

Signs it needs replacing

• Battery light on the dashboard
• Battery keeps going flat
• Headlights dim and brighten with revs

What to tell the shop

• Vehicle make, model and model year
• Engine size, and whether it is manual or automatic
• The number printed on the old part, or a photo of it
• Whether you want genuine, OEM or a local replacement