A sharp decrease in the brightness of the light beam most often indicates oxidation of the contacts in the lamp cap or degradation of the reflective layer inside the headlight itself, which requires immediate intervention for safety. When you notice that halogen LEDs have stopped breaking through the darkness the way they used to, which doesn’t always mean it’s time to buy new equipment. In half of cases, the problem lies in the banal drop of voltage in the onboard network or contamination of the transparent part of the lens, which are easily eliminated in garage conditions.
Primary diagnosis should begin with checking the voltage at the battery terminals with the engine running and the passing light on, since the generator may not cope with the load.
If the voltmeter shows values below 13.5 V, then dim light is a direct consequence of undercharging, and you need to look for a malfunction in the charging system, not in the optics.
In a situation where the tension is normal, but xenon or halogens shine weakly, you should pay attention to the state of the body mass and the integrity of the insulation of the wires going to the ignition blocks or caps.
The main causes of the deterioration of light flux
One of the most common reasons why headlights are getting badIt is a natural ageing of incandescent lamps. The tungsten thread becomes thinner over time, and the evaporating metal settles on the walls of the bulb, creating a dark coating that significantly reduces light output.
The second critical factor is the clouding of polycarbonate glass. Under the influence of ultraviolet light and abrasive dust from the road, the surface becomes matte, scattering light in different directions instead of forming a clear beam.
Also, you can not discount the oxidation of contacts in the cartridges, especially if moisture got into the headlight housing, which leads to heating of the connection and a voltage drop on the lamp itself.
- 🔦 Burning of tungsten filament and blackening of lamp bulb.
- 💧 Moisture entering the housing and oxidation of the reflector.
- ⚡ Oxidation of terminals and connectors of wiring of the car.
- 🌫️ Microcracks on glass that scatter the light flux.
⚠️ Note: Operation of a car with a faulty head light is prohibited by traffic rules and can cause an accident at night.
Diagnostics of electrical circuit and voltage
Before changing the light bulbs, you need to make sure the stability of the power supply, since even a small voltage drop drastically reduces the brightness of the glow of the filament. Use a multimeter to measure the voltage directly on the cap contacts when the light is on; if the difference in voltage on the battery exceeds 0.5-0.7 V, then there is a high resistance in the circuit.
Often the culprit becomes the culprit. headlightcontacts inside which could burn from frequent switches or surges of current. Replacement of relays is an inexpensive procedure that often returns the standard brightness of the lighting without replacing other components.
Special attention should be paid to the "mass" of the body, since poor contact of the negative wire leads to the fact that the current goes along the path of least resistance through other nodes, causing their heating and unstable operation of the optics.
Voltage standards in the on-board network
When the engine is running, the voltage should be 13.5-14.5 V. If it falls below 13 V when the headlights are turned on, check the tension of the generator belt and the state of the battery terminals. A critical value is below 12 V, at which the light will be dim even on new lamps.
The integrity check of the wires shall include a visual inspection of the rubbing of the metal partitions.
If you've installed LED lamps Instead of regular halogens, make sure that the control unit or resistors are connected correctly, otherwise the system may produce an error or decrease brightness.
Restoration of transparency and headlamp cleaning
If the electrical part is fine but the light is still weak, the problem lies in the optics, which has lost transparency due to long operation. Polycarbide glass clouding is a chemical process of degradation of the upper layer under the influence of sunlight, which can be eliminated by polishing.
For deep restoration, you will need to remove the headlights, seal the body with paint tape and go through several stages of sandpaper with different grains, ranging from the P800 to the P2000 or P2500.
After machining, the surface must be polished with a special paste and a protective varnish or film is applied to ensure that the result lasts for several years.
- 🧼 Careful washing and degreasing of the surface before the start of work.
- 📏 Grinding with abrasives with a gradual decrease in graininess.
- ✨ Machine polishing using a soft sponge.
- 🛡️ Applying a UV protective layer or armor film.
☑️ Checklist for headlamp polishing
There is a chemical recovery method that is faster than mechanical, but requires caution when working with vapors.
The use of reducing agents based on ethyl acetate allows you to quickly remove yellowness, but without subsequent protection, the effect may disappear after six months.
Condition of reflector and interior
Inside the headlight is a reflector coated with a thin layer of aluminum or chromium that forms a beam of light, and if this layer is damaged, the light will scatter chaotically. Owners often notice that headlights are getting bad It is due to the burnout or detachment of the reflective coating, which is especially characteristic of old halogen and xenon systems.
The cause of reflector degradation is often the installation of high-power lamps that emit more heat than calculated by the manufacturer. High temperature leads to melting of the plastic base and loss of geometric shape of the reflector.
| Type of damage | Signs. | Method of decision |
|---|---|---|
| Burnout of coating | Dark spots on the reflector | Replacement of reflector or headlamp assembly |
| Fogging | Condensation on the glass from the inside | Drying, replacing seals, checking the sapunas |
| Mud inside | Dust on the lens or reflector | Disassembly and cleaning of the shell |
| Plastic cracks | Fractures from stones, violation of tightness | Plastic soldering or glass replacement |
Tip: When installing more powerful lamps, be sure that the base and wiring will withstand the increased current load, otherwise the risk of fire in the hood space will increase significantly.
If dust or insects are visible inside the headlight, this indicates a leakage violation, which also leads to the settling of dirt on working surfaces.
To clean the insides, the headlight often has to be heated in an oven or a building hairdryer to soften the sealant and detach the body.
Effect of lamp type on lighting quality
The choice of light source plays a key role in how effectively the road is illuminated, and different technologies have their own degradation features. Halogen lamps lose brightness over time due to changes in the chemical composition of the gas inside the bulb, whereas xenon can dim due to the aging of the electrodes.
The most effective solution today is the installation of high-quality LED modules. which provide stable brightness throughout the service life, but require good heat sink.
When switching to LEDs, it is important to consider light distribution: cheap lamps can blind oncoming drivers if they do not have the correct focus in the reflex headlight.
- 💡 Halogen: Cheap, but quickly dim and warm.
- 🔆 Xenon: Bright light, but requires block ignition and washing.
- 🔷 LEDs: Long-lasting, do not heat the headlight, but are sensitive to crystal overheating.
- 🌕 Laser headlights: Maximum range, high cost.
⚠️ Warning: Installation of lamps with a base not corresponding to the type of headlight (for example, LED in a reflector under a halogen without a lens) can lead to improper light distribution and blinding of other road users.
Light adjustment and final check
After replacing the lamps or restoring the headlight, adjustment of the light beam is mandatory, since even a slight displacement can reduce the lighting efficiency by 40-50%. Proper adjustment provides not only comfort to the driver, but also the safety of oncoming transport, eliminating the risk of blinding.
The adjustment procedure can be carried out independently on a level platform in front of the wall, using the markings according to the instructions for your car model, or contact a specialized stand.
Do not forget to check the work of the headlight corrector, if it is provided by the design, since the jammed drive can lower the light too low, creating the illusion of poor lamp operation.
The comprehensive approach – replacing lamps, polishing glass and adjusting correctly – returns 90% of efficiency to light, even on older cars.
Be sure to wipe the outer surface of the headlight clean before the final test, as a thin layer of road film can imperceptibly reduce brightness.
Check the high beam: if the near light is good and the far dim, the problem may be the burnout of the second thread or switch on the steering wheel.
Why are the new lamps dim?
New lamps may shine dimly due to defective base, loose fit in the cartridge or incompatibility with the headlight reflector. Also, the reason may be the low quality of the lamp itself (a Chinese brand with overrated characteristics on the packaging).
How often should the headlights be polished?
Pollination is required as the clouds become cloudy, usually once every 2-3 years of active operation. Frequent polishing thins the plastic, so after each deep grinding, it is recommended to apply a protective layer of varnish or glue the film.
Can I put more powerful lamps?
Putting lamps more powerful than regular ones (for example, 100W instead of 55W) is dangerous: the plastic of the headlights melts, contacts are oxidized and the risk of fire increases. It is better to replace the standard lamps with quality analogues with improved performance (Plus 50%, 90%).
What to do if the headlight sweats from the inside?
A small condensate that disappears after turning on the light, for example. If the drops are large and do not disappear, the tightness is broken. You need to find a crack, replace the sealant or sealant of the junction of glass and body.