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Headlights are simple plastic boxes made up of two halves. The back half is black plastic and the front half is a clear plastic lens. These two halves are glued together to form a module for the headlamp bulbs to be placed in.
Headlights tend to build up with condensation when they are exposed to a higher level of moisture than usual and when the exterior is colder than the interior of the lamp. It is more common in colder months. However, if there are excess amounts of condensation then there could be an underlying issue with headlight itself.
Over the time, our car’s headlights may show signs of fogging, condensation, discoloration, and other effects that reduce brightness. These are signs that our headlights need to be checked & resealed.
COMING TO GENERAL QUERIES …
A. Is the headlight assembly completely sealed against air & moisture?
Answer: NO! These modules are NEVER sealed. If we attempted to seal one, it would have to explode upon use, as the heat generated by the bulb must be dissipated. The halogen /led bulbs that headlights use get much hotter. As they get hot, they heat the air around them that then expands and has to have a way to escape the headlamp module or else it would try to blow up like a balloon.
Same when we shut it off. The air around the bulb contracts and if the housing were sealed, it would implode due to the surrounding pressure outside of it.
B. How & Why water droplets appearing inside the headlight housing?
Answer: Firstly, we have to differentiate between moisture and a whole bunch of water.
The Automobile manufacturers say that some moisture was normal due to the humidity being drawn inside as it cooled. And the fix was to turn the headlamp on! As it heated and the air expanded, the moisture would disappear.
Most all of these housing is vented on both the top and the bottom. This allows the moisture and air to get in and out quickly. When they are vented on the top, they often have a little rubber vent tube or a shielded vent hole to prevent excess water from entering when you drive in the rain.
When bunch of water if noticed, it can’t be ignored.
Need to examine:
1. Ineffective seal: Butyl / Silicone seals are designed to keep out moisture, so any damage can result in water working its way in.
2. Vent problems: The inbuilt headlamp vent is there to regulate air pressure within the headlamp, and so vent blockages can impede this process.
3. Damage to headlight: Any cracks or damage can allow in excess moisture & water.
C. Will silica gel packets work? Is there any other way to quick dry out the moisture?
Answer:
1. To dry it fast, some try to keep a couple of small bags of desiccant to the inside of the rear cap or even drop it inside through the bulb hole by tying it with a thread.
2. Some other try to warm the lens using a hair drier.
3. Some remove the parking bulb, make the socket open to facilitate moisture to evaporate by switching on the high-beam headlights for 10 to 15 minutes.
4. Some remove the bulbs and connectors. Spray compressed air into the housing to remove the moisture & to clean out the vents if they are blocked.
5. Some even drill a hole below the housing to facilitate drainage.
It may or may not help as it depends upon the quantity of water drops and source of leakage. Mostly it might be a temporary effort. It is always better to find the root cause and tackle it to avoid reappearing of the issue.
E. Headlight Condensation – Dos and Don’ts?
Answer:
1. Do not wash the car immediately when the engine bay is hot.
2. Do not wash the Headlight/Fog Lamp or any car lamp assembly with extremely super force water jet.
3. Keep the Headlight assembly, Dust caps, rubber sealers and rubber boot/vent tubes clean & dust free periodically.
4. If moisture is noticed inside, examine thoroughly for crack, the condition of the original sealant (joint between the lens and rear housing), gaskets on the bulb assembly, rubber sealers whether missing or damaged, whether rear cover incorrectly fitted, etc., Apply a layer of sealant (RTV - Room Temp. Vulcanizing) Butyl or Silicone Sealant where the glass links the housing or on suspected joints / crack.
5. Check Vents blockages : There is no need to drill a drain hole at the bottom of housing as per old practice; the OE headlights do have an inbuilt venting system to take care of minor condensation - when they are vented on the top, they often have a little rubber vent tube or a shielded vent hole to prevent excess water from entering when you drive in the rain.
6. Take extra care on rubber washer which comes within the cap behind the headlamp whenever we replace a fused or a better bulb, as it is another common cause to notice condensation after bulb replacement.
7 Either replacing the housing or removing it completely for a total cleaning and overhaul is the only way to stop the major buildup inside the lens.
Also
8. Don’t miss to check the headlights while taking delivery of a new vehicle as they might have been kept in open yard for many days/months, subjected to instant washing before delivery.
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