First, determine what the problem is. Are they dim, not working at all, hard to see with at night, have water inside, failed inspection? If they don’t come on at all either you have a burned out bulb or an electrical problem. An electrical problem can be expensive and very labor intensive to fix – but they are usually vary rare. So lets first look at the bulb. The bulb unscrews out of the back of the headlight lens on most newer cars (on older cars with glass headlights the whole lens is the bulb and you just replace it with a new glass replacement $10 – $20 at Walmart). After removing the bulb, look at it. Does it look burned out? Is it black, melted, discolored? If so, replace with a new one. You can purchase replacements at your local automotive store or Walmart for under $20. Insert the new bulb or bulbs and make sure not to touch the glass part of the bulb with your fingers – the grease we emit on our fingers will cause the bulb to wear more quickly or even blow. After installing the bulb try the lights. 99% of the time this is the reason they will not turn on. If it still doesn’t light you have an electrical problem and this should be referred to your local mechanic.
If you have water in your lens this is caused by a leak, crack, or hole in the lens. With the newer plastic lenses you need to remove the lens and then carefully drill a small hole into the bottom of the lens (be careful not to hit the bulb. Let the water run out and then patch with silicone (easily obtained at Walmart or your local automotive store). Then find the source of the water. Usually the seals start to go bad after 3-5 years. You can cover the seal around the lens with silicone to reseal the lens. If the leak was caused by a crack a clear sealant like urethane can be used to seal the crack or small hole. If it is a large hole it would be best to replace the lens.
The other major problem is cloudy, yellow headlight lenses which can lead to diminished output, poor nighttime visibility and basically an unsafe car. There are now headlight repair, restorer and cleaner kits available to cure this problem. In the past you had to resort to replacing your lenses which can be very expensive – $200+ per lens not including installation and labor at your local car dealer. Now for under $20 you can fully restore your headlight lenses to like new optical clarity and greatly improve your nighttime safety. For more information on these kits please see the link below.
There you have it – the three biggest problems with automotive headlights and how to fix and repair them for greater safety for nighttime driving – and save big by doing it yourself. Please take the time to make your headlights and rest of your car as safe as possible. As having volunteered for a volunteer emergency squad for years I have personally witnessed dozens of fatal crashes that could have easily been avoided by just properly repairing and fixing the headlights. Be safe, drive safe – remember the life you save may be your own. Please pass this around so that it may benefit as many people as possible and increase the safety on our roads.