Do headlights NEED breathers?

[NoodleFace]

Do headlights really need breathers. Those rubbery nob-like pieces on the back of the housing. What would happen if they didn't exist and the housing was fully sealed?
I'm interested mainly because I want to convert a pair of ruined 7" sealed beam housings to something that has a plastic lens, a bixenon projector and a sealed serviceable back. But seeing as to how I am lacking in the vent/breather knowledge department, I may as well know what I'm getting myself into. What drawbacks if any would I face if I didn't install one? And if they're necessary, is there a diy guide out there or do I have to retrofit one?
Any suggestions concerning the retrofit itself are also welcome.

[satrya]

My day job isn't designing automotive headlights, but I've had interest in this topic in various past threads. I haven't seen (either first hand or from forum posts) OE housings for low beams (i.e. I'm excluding lower power sealed units for things like sidemarkers or turn signals) that don't have a vent. My assumption has been that since low beam units generate high enough heat (either mostly radiated on the same side as the beam like halogens and HIDs or on the back end like LEDs) that the change in air pressure may be big enough to instigate a small leak. And when the negative pressure induces leak, it could take in moisture which due to the sealed nature, would not be sufficiently evacuated even when the temperature inside rises again. As a result, it is best to provide the atmospheric vent to hasten this equilibration.

Of the housing's I've seen, including small housings that are meant to weather proof auxiliary foglights, they have some means of small vent opening somewhere.

In one of my custom housings, I added a ~ 1/16" tubing that points down on the back end of the housing. The rationale is that under normal conditions, water splashes won't go up the tube, but excess moisture can equilibrate quickly. But I found that 1 of the housing pairs see condensation on the lens in rainy days. It is possible that the cause is more because of my custom housing not being watertight in other parts instead of the flaw in the breather tube, thus allowing more moisture to come in from the ground on rainy days than what the tube and the increase in temperature (from the halogen bulbs) can take care of.

[NoodleFace]

But we already know a headlight housing that's not sealed properly will show condensation on the inside of the front lens. Wouldn't a breach in the housing in the form of a vent tube still cause the same? Is the vent some sort of one-way valve that opens at a certain pressure?

[evo77]

Condensation will always occur when the right conditions are present. Even with a fully sealed housing. Check out this bulletin from 2015 that JW Speaker sent out to their dealers which advised customers to accept condensation as a normal occurring thing and that it does not impact lighting performance.

Breathers and vent tubes are a form of proper ventilation for headlamps and are usually placed at strategic locations of the back housing. This facilitates the drawing in of cool air and evacuation of hot air.

Many variables will come into play with condensation but the main focus is where the radiant heat from the light source reaches within the enclosure. Often the coolest point of the lamp is the weakest point which is typically at the very bottom of the front lens, which can also be an area where even the rays of the sun do not reach. Heat from the light source does not reach that area and cannot properly evaporate the condensation. Inadequate air flow along that lower region also contributes to the trapped moisture.

This phenomena can be difficult to prevent but it can be solved by means of physical testing and computational analysis. It is a rather expensive and time consuming process, which some car makers skimp on in order to save money. And this is why we still see cars today with foggy headlamps, like the xenon lamps in our 2019 Durango R/T.

From a retrofit perspective this opens a new can of problems because you are assembling of bunch of different parts together that were never designed to be together in an unconventional method unaware of how air flow and natural convection is occurring within.

[NoodleFace]

Your last paragraph there almost made me change my mind. I still want to go ahead with it for science Also because I'd be combining ruined headlights with my old craptacular projectors.

It's for a friend's gen 2 golf and he doesn't have enough cash or time to be experimenting on his headlights only for them to fail soon after. So my idea was to make the insides accept any projector so that when I finish dialing in the body (vents included) we can spend the doe on a decent kit. Till then it's craptacular projector and cheap HID kit ftw.

So with that in mind I hope you understand I value any advice given with how to move forward.

[NoodleFace]

Ok so I took the hint and went to browse some of the older threads on here taking about vents. But I can't really tell if everyone agreed on a certain rule of thumb regarding placement and count of these vents.

TRS's website recommends theirs be placed in the upper half. Lightwerkz suggested one of their clients drill holes beneath the projector.

So far I know I probably need vents. I say probably because my project involves a relatively small housing and the main heat source will be very close to the front lens.

One more question, is there a reliable way to test my work without having to wait for a 12 month field test?

[evo77]

These are the downfalls of retrofitting lamps. Devising a proper ventilation system without proper equipment or knowledge requires more than just "guesses" about where holes and plugs are placed.

There is no template for this because each lamp and each situation is different. And I can assure you there is no "process" that retrofitters use to address this situation other than maybe sticking those silica packs inside. Most believe that condensation is because of an improper seal around the lens rather than understanding the workings of air flow within a lamp.

Anyone can come in this thread and make recommendations about where you could place your vents but again, they are just guesses. They may or may not work.

If your determined about doing these lamps than your going to have to just trial and error it unfortunately.

Ay
IA

[NoodleFace]

Ok so looks like trial and error it is going to be unfortunately. But I still have a couple of unanswered questions if you guys may. Would a volumetrically small enclose fair ok being completely sealed? How can I bench test all that?

A thought that hit me earlier today as well; if the problem is with the water content in the air inside the headlight then why wouldn't OEMs just pack the headlights with dry air and completely seal them, no venting, the works. I cannot be the only one that thought of this. Would apply to full LED only I suppose since they are non-serviceable units.

[evo77]

Check out these links to learn more about how/why condensation occurs and the workings of headlamp ventilation.

Link 1
Link 2
Link 3

[NoodleFace]

Thank you very much. These definitely need a clear head and a mug of coffee.