Car trouble · Lights & electrical

My dashboard lights dim or flicker

The dash lights, headlights or radio dim and brighten, often with the engine running. That usually points to the charging system.

Get to it this week

A starting point, not a diagnosis. Most parts stores read check-engine codes and test batteries for free.

Likely causes — tick the parts you want

  1. A failing alternator

    most likely · Doable with tools and a free afternoon

    How to check: Watch for a battery warning light while driving, and whether the lights brighten when you rev the engine. A free charging-system test at most parts stores will confirm it.

  2. Loose or corroded battery connections

    possible · Most people can do this

    How to check: With the engine off, try to wiggle each battery clamp and look for crust on the posts. A loose clamp causes flicker that comes and goes over bumps.

  3. A worn or slipping serpentine belt

    less likely · Doable with tools and a free afternoon

    How to check: With the engine off, look at the belt that turns the alternator. Cracks, shiny glazed sides, or a squeal on startup mean it may be slipping.

Be careful

Wear eye protection and gloves around a battery — it holds acid and can give off explosive gas. Take the negative (black, minus) cable off first and put it back on last, and never let a metal tool touch both posts at once.

Your car — the counter needs this

If the counter doesn’t have a part, your shopper asks them to order it under your name and messages you the order number. When it comes in, send someone to collect it.

Not quite it?

My headlight is outMy brake light is outMy turn signal is blinking fast
My dashboard lights dim or flicker — likely causes and the parts · DriverRuns