How To Seal A Headlight

In this article, we’re going to show you how to seal a headlight on your car. 

Moisture and condensation are the most common issues that give rise to blowing headlight bulbs and electrical system shorts in your vehicle’s electrical system.

Unless the bulb or bulbs blow straight away, this might not manifest as an immediate problem, but over time it can cause your headlights to dim, and create issues with visibility at nighttime and in hazardous weather.

Making sure your headlight casings are properly sealed, is one way to make sure you limit the risk of moisture getting into the headlight system. Here follows some handy hints and valuable information to keep you driving safely at night.

What You’ll Need To Seal A Headlight

Any maintenance on your headlight system is probably the easiest DIY task you could undertake on your vehicle. There’s really nothing to it.

To seal a headlight unit, you’ll need the following tools and consumables:

  1. 1000-grit wet/dry sandpaper
  2. 2000-grit wet/dry sandpaper
  3. 3000-grit wet/dry sandpaper
  4. Polishing compound
  5. Paste wax
  6.  Roll of painter’s tape
  7. Microfiber towels
  8. UV sealant

That’s it! With these in hand, you’re ready to read on and follow the easy step-by-step instructions below.

How To Properly Seal A Headlight

First, make sure that the problem you have with your headlight has its origin in the headlight unit itself. Look for micro-cracks, or cracked seals around the edges.

Then, open the hood and start to remove the screws or clips that hold the headlight enclosure to the bodywork of the vehicle. If you’re not sure about this, check your owner’s manual. There should be a section on headlights that will contain all the information about the clips and screws you may need.

Wash the polycarbonate plastic of the headlight

This is really important, and you may as well do it while you have the whole headlight system disassembled. Once you’re done with the cleaning process, make sure the whole enclosure is completely dry.

Sealing fissures

If you picked up any cracks or fissures in Step One, this is where you apply a simple repair to those. Your headlight sealant goes to work here. A thin piece of cardboard or even the edge of a credit card comes in handy to work the sealant into the fissures and cracks. Once you’ve sealed everything, let it stand for around 30 minutes to dry, before reassembling it.

Method two – works for a sealed unit

If your headlight is a sealed unit and disassembly is impossible, drilling a small hole in the bottom end can help prevent condensation and accumulation of moisture. Drill a hole in the bottom of the headlight unit. Then drain out the water, and seal the hole with your sealant.

Removing moisture without opening the unit

These are hacks if you want to solve the moisture issue without removing the entire headlight assembly:

  1. Waiting for it to dry – this will work if you’re dealing with a thin film of moisture, or a few droplets of condensation. If the water is pooled in the bottom of the headlight enclosure, though, this may not be the best method.
  2. Use a good old hairdryer – heat the exterior of the enclosure until the water evaporates. The air will escape through the air vent, taking the moisture with it. Make sure you set the hairdryer at low heat, however. Otherwise, you stand a chance of damaging the headlight enclosure.

Signs you may need to seal your headlight

Headlight fog is a sure sign you have a moisture leak into your headlight enclosure. This fog can simply be in the form of a mistiness on the inside of the assembly, or it can be a film of water droplets. Either way, when you notice this, make work of it. If you don’t chances are good it will eventually cause an electrical short, and this could mean bigger expenses.

A parting shot

Headlights are crucial for your safety when driving at night, and for the safety of other road users too. They’re a lightweight, DIY maintenance item and should be inspected at least once every eight weeks to make sure the bulbs and lenses are in proper condition. They’re inexpensive and easy to maintain, even if you don’t have any technical experience. Imagine – they could save your life!

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Richard Nickleson is the author and owner behind Headlight Reviews. He first started the site as a hobby to share his insights on car parts and specifically headlight bulbs, but it soon ballooned and now he writes on all topics surrounding headlights bulbs. If you've got a bulb question, contact Richard here.