Condensation inside your headlight is bad news. The buildup of moisture leads to premature bulb failure and can lead to electrical short circuit on certain models. Sure you could take the easiest way out and drill a drain hole in the headlight lens, but that just looks ugly and doesn't solve the real problem. To permanently get rid of condensation, you need to reseal the headlight completely.
If condensation buildup came on suddenly after a recent repair or headlight bulb change, ensure that the the cap holding the headlight bulb -- the rubber cover that conceals the access hole for the bulb -- is secured and properly sealed. Replace any gaskets for the cap as needed.
It may not be possible to reseal your headlight. If there is no way to remove the front lens cover as suggested in the following steps, you'll need to replace the headlight assembly.
Things You'll Need
- Heat gun
- Flathead screwdriver
- Razor scraper
- Fine wire brush
- Streak-free glass cleaner
- Microfiber towel
- Clear RTV silicone
- Vehicle-specific service or repair manual
Step 1: Remove the Headlight from your vehicle.
On some models, you may have to remove the front bumper cover to access all of the headlight's retaining bolts. Follow directions in your vehicle's service or repair manual for assistance in removing the headlight assembly, if needed.
Don't touch the glass portion of your headlight bulbs with you bare skin -- oils from your skin will remain on the bulb and cause premature failure.
The front bumper cover is normally secured to the vehicle with a number of plastic retainers, screws, metal clips and sometimes bolts. Look along the top of the grill, along the bottom of the bumper cover and inside the wheel wells for all of these retainers.
Step 2: Separate the lens from the headlight assembly.
Look around the assembly, where the clear lens meets the rest of the assembly. You'll see there are locking tabs that can be lifted up to separate the two, but don't try just yet.
The lens can break easily when being separated. Failure to follow the rest of this step precisely may result in damage to the lens.
Set a heat gun on the medium setting and begin sweeping the stream of hot air over the top of the headlight lens, where it joins the assembly, for at least a minute. Quit applying heat when the lens becomes hot to the touch. Pry up each locking tab and gently push the top of the lens away from the assembly -- just enough so that the lens doesn't lock back into place when you remove the screwdriver. Work your way around the headlight heating and pry each locking tab until all are unlocked. Continue heating around the assembly as you separate the lens from the assembly.
Don't concentrate the heat gun stream in any one place for too long, or it will melt or discolor the clear lens.
Step 3: Remove all old sealant and adhesive.
Clean all of the old sealant and adhesive from the headlight lens and the assembly. You should be able to get most off with a razor scraper, but you can use a wire brush for the tough spots. On real difficult spots, use extra fine-grip sandpaper, but be careful not to scratch the inside of the lens or deform the mating surfaces.
Chemicals and clear plastics don't mix well. Do not use any type of adhesive remover, nail polish remover, brake cleaner or any other substance that can break down glue, as it will also damage the headlight lens and possibly the assembly.
Step 4: Clean the lens.
Use glass cleaner and a microfiber towel. Ensure that there is absolutely no leftover dust or other contaminates from removing the old sealant. The lens should be crystal clear before continuing. Wipe the mating surface on the other part of the headlight assembly with glass cleaner as well. Ensure that both mating surfaces are completely dry before continuing.
Hold the lens at different angles to expose any streaking that you may not see right away. Wipe away any streaks with a dry cloth.
Step 5: Assemble the headlight.
Apply a thin bead of clear RTV silicone to the mating surface on the headlight assembly. Exercise caution when applying the silicone -- too much will cause the silicone to overrun into the headlight, but too little will prevent a good seal and lead to more condensation. Press-fit the lens onto the headlight assembly and ensure that all locking tabs lock into place.
Step 6: Install the headlight assembly.
Reverse the procedure given in your vehicle's service or repair manual to install the headlight and bumper cover, if needed. Follow all torque specifications given for the headlight and bumper cover bolts. Don't turn on the headlights until you've allowed the proper amount of curing time recommended by the manufacturer of the clear RTV silicone.