How to Repair Dim Headlights
Updated: Apr. 18, 2024
Headlights showing signs of age? Repair dim headlights yourself with these tips.
Time 2 hours
ComplexityBeginner
Cost$10 and up
Introduction
Dim headlights pose a danger to yourself and others. If yours are not as bright as they used to be, it's time to determine why. Many scenarios lead to dim headlights and sometimes the answer to fixing the issue is simply to buy new headlamp bulbs. But before you spend any money let's check other contributing factors off the list.
What Causes a Dim Headlight?
Headlights naturally dim as they age, but poor wiring, rusted ground connections, and old, dull headlight housings can worsen matters. Headlight filaments deposit a gray/brown film on the inside of the bulb as they age and over time that coating can reduce luminosity by up to 50 percent!
If the bulbs are new, but the headlights are still dim, it's time to check the ground connections and the headlight lens itself. If one or both headlights flicker when going over bumps, there's probably a corroded wire or bad connection somewhere along the line.
Ahead, you'll find simple tips to help you repair dim headlights for good.
Tools Required
- Adjustable wrench
- nitrile gloves
- Screwdriver
- Wire brush
Materials Required
- Dielectric grease
Project step-by-step (6)
Inspect the headlight housing
- The first thing to check off the list is the headlight housing — a brand-new headlamp bulb won’t help if the plastic headlight housing is deteriorated.
- If the plastic is foggy or has a dingy yellow tint to it, it’s time to restore the headlight.
Check the headlamp bulbs
- Check both bulbs to see if the inside of the glass is showing signs of age.
- If there is a brown/gray film on the inside of the bulb, it’s time to change them.
Clean the headlamp connections
- Disconnect the plug from the rear of the headlight housing.
- Remove any corrosion or rust with a wire brush.
- Spray electrical contact cleaner on both connectors and re-attach.
Clean ground cable connections
- Trace the wiring harness from the back of each headlight assembly and find where it connects to the vehicle body.
- Remove the bolt. Clean it with a wire brush, including the spot on the chassis, and re-attach.
- Coat the parts with dielectric grease to guard against corrosion.
Are your headlights still dim?
- If you’ve gone through all of the above, and you’re still not satisfied, you might need to adjust your headlights.
FAQs
Do headlights dim over time?
Yes. Even the most expensive bulbs lose their power over time.
How long do headlight bulbs last?
That depends. Hours of usage, battery health, type and brightness of the headlamp all play a part.
How can you prevent dim headlights?
Replace your headlamps on a regular basis, inspect your electrical connections seasonally, and restore or replace the headlight housing if the plastic is faded.
Why are headlights still dim after replacing the bulb?
Poor ground connection to the chassis, poor battery health and faulty wiring can all be contributing factors, but most often it’s a fogged or yellowed plastic headlight housing.
How much does it cost to replace headlights?
New headlight housings can cost up to $200 each, while just replacing the headlamp bulbs within the housing (most typical) will cost between $30 to well over $100 for a pair, depending on brightness and type of bulb.
Should you replace both bulbs at the same time?
You don’t have to, but it just makes sense. Whenever I swap one, I swap the other. This way, the luminosity is equal on both sides and should remain so throughout the life of both bulbs.
Do HID and LED headlight bulbs dim over time too?
Yes, as they age, HID (High-Intensity Discharge) and LED (Light Emitting Diode) bulbs will dim, but this happens much more slowly than with filament type bulbs.
Looking for more options?
Get to know the difference between LED and halogen headlights.
About the Expert
Jay Cork, a self-taught mechanic and former manager of an O’Reilly’s Auto Parts store has chased more wiring gremlins than he cares to remember.
Originally Published: November 26, 2018
