Car Headlight Condensation – Issues & Solutions


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Dr MUDHAN

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Condensation headlight.jpg


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.



Headlight Condensation.jpg



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Dr MUDHAN

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F. How to choose a good headlight sealing adhesive?

Avoid choosing hard to crack adhesives like Araldite (Epoxy resin), or Super Glue/ Fevikwik (Cyanoacrylate) as it reacts with some plastics.
A flexible adhesive like Room Temperature Vulcanizing (RTV) silicone gasket sealant are better. But the best product depends on the type of headlight design based on whether its surface is smooth or not.
The bonding should be able to take up the stresses of heating and cooling, also the vibration while driving.

These are some of the bonding agents preferred by professionals:

Silicone Headlight Sealant (Example: Loctite 395)
It’s flexible so that it won’t crack or peel due to harsh weather.
Silicone can be messy, so applying sealant with no gaps is essential.
The silicone sealant takes about 24 hours to set and dry thoroughly.

Polyurethane Headlight Sealant (Example: 3M 590)
High adhesion to smooth surfaces.
Repairs can be carried out in various weather conditions, so it’s relatively easy to glue the headlight in the open (rather than in a garage or workshop).
Polyurethane is soft and sticky, so handle it with care. Drips can be challenging to remove.
It’s mostly used for commercial purpose; single-use DIY packaging difficult to get..

Butyl Tape (Example: Retro Rubber Strips)
It’s a rubbery bead that is easily applied by packing it into an existing groove in the headlight housing.
It is a thermoplastic elastomer - Polyisobutene that creates a strong bond and doesn’t degrade over time.
Butyl headlight sealer is the most frequently used in DIY applications, over silicone headlight sealer.



G. How to Reseal a Vehicle Headlight?

Resealing the existing bond is not difficult. Remove the headlight - Clean the old sealant from the channel - Sand the channel with sandpaper to improve adhesion - Apply the sealant around the light’s outlines leaving no gaps - Apply low heat with a hair dryer - Hold for a few seconds until the sealant sets. Wipe away any excess sealant with a damp cloth. Take care, do patiently as Drips can be challenging to remove.

Complete overhauling requires professional help. Headlights that were glued shut can be tricky to open. Proper application of heat to break the seal and opening into two halves without causing any further damage is important .

Headlight Sealants.jpg
 
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Thread Starter #3

Dr MUDHAN

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H. Headlight Condensation – Can it be claimed under Manufacturer’s Warranty for replacement of the defective unit?

CAR HEADLIGHT ISSUES.jpg


Answer: Yes & NO !

NO – Service Station Remarks:
Vehicle exterior lamp assemblies are fogged with a light layer of condensation on the inside of the lenses. If happen occasionally, and -
  • Reported after the lamps have been turned ON and brought up to operating temperature, turned OFF, and then rapidly cooled by cold water (such as rain, or the water from a car wash.
  • Vehicle has been parked outside overnight during a warm humid day followed by clear cool night. Turning the lamps on will usually accelerate, allow the condensation to change back into a vapor.
A lamp that exhibits condensation/fogging should be evaluated in a service bay environment by first drying all water from the outside surface of the lens and operating the lamp for 20 minutes. If the condensation/fogging has begun to clear from the lamp lens after 20 minutes with the lamps operating, this indicates the lamp sealing has not been breached, and the lamp does not need to be replaced.

YES – Service Station Remarks:
If the condensation/fogging has not begun to clear after 20 minutes with the lamps operating, or the lamp has large amounts of water droplets visible on most internal surfaces, or moisture in the lamp is always present and never disappears. It indicates a problem with the lamp sealing that has allowed water to enter the lamp. A lamp that exhibits internal moisture permanently should be replaced.



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Please do not miss to read main thread, the ultimate guide for more in-depth information:
Car Head Light Restoration Guide
 
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Our forum member has shared his beautiful DIY and how did he overcome the headlight condensation issue in his car.
No sir, my car didn't have any condensation issue since day 1. Apologies if my post conveyed it that way.

It was opened to retrofit Morimoto HID projector setup as against the OEM halogen projectors. I only explained the method I followed to open and re-seal the headlights to avoid any condensation or water ingress issues while washing.
 
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