My headlights are dim and sometimes flicker
If the lights get brighter when you rev the engine, the charging system is weak. That is usually the alternator, a loose or corroded battery cable, or a bad ground. If the lights just look hazy, the lenses may be yellowed from the Florida sun or the bulbs are old.
Urgency
This week is fine
What to do right now
What to do right now
- 1Rev the engine a little in park and watch the lights. Brighter with revs points to charging.
- 2Watch for a battery light or a slow crank in the morning. Either one means come in today.
- 3Look at the headlight lenses in daylight. Cloudy yellow plastic cuts a lot of light.
- 4Limit night driving until it is checked, especially in the rain.
What it usually is
What it usually is
Starter and alternator
A weak alternator cannot keep up with the lights, AC, and fan at night. We test its output under load.
See the serviceBattery replacement
A dying battery or corroded terminals can make lights dim at idle. Miami heat shortens battery life.
See the serviceElectrical repair
Flicker with good charging often comes from a bad ground or a loose connector in the headlight circuit.
See the serviceQuestions people ask
Is it the bulbs or the alternator?
If both headlights are dim the same way and the dash lights dim too, it is usually charging. If one side is dimmer, it is often the bulb or the wiring on that side.
Why are my headlights yellow and foggy?
The sun breaks down the clear coat on plastic lenses. In South Florida it happens fast. Restoring or replacing the lenses brings back a lot of light.
Can a bad alternator leave me stranded?
Yes. Once it stops charging, the car runs on the battery until it dies, sometimes in less than an hour. Do not wait on a battery light.
Will new bulbs fix it?
Only if the bulbs are the problem. New bulbs on a weak charging system will still be dim. Test first.