Fog lamp

Fog lights improve road visibility in fog, heavy rain, snowfall and spray. For MAN and Mercedes trucks, buses and vans, they form part of the lighting circuit and are often integrated into the bumper, front panel, headlamp unit or separate lamp bracket. A correct beam pattern is essential: fog lights must shine low and wide, with a sharp upper cut-off to limit reflection from water droplets and glare for oncoming traffic. The correct part is always determined using the vehicle chassis number. Visual comparison or selection based on the model name alone is never sufficient, as bumper versions, connector pin configurations, lighting functions and vehicle wiring may differ.

Fog lights are fitted to, among others, the MAN TGL, TGM, TGA, TGS, TGX, TG3 and TGE, as well as older F90, F2000, M2000 and L2000 series. For Mercedes, they are used on models including the Atego, Axor, Actros, Antos, Arocs, Econic, Sprinter, Vito and V-Class. Buses such as the MAN Lion’s City, Lion’s Coach, Mercedes Citaro, Intouro and Tourismo, and the Neoplan Cityliner or Tourliner may also use specific front lighting.

There are halogen fog lights with H1, H3, H8, H11 or H16 bulbs, LED fog lights with an integrated light source, and combined units with fog lights, daytime running lights or cornering lights. The electrical system is generally 24 V on trucks and buses, while vans use a 12 V system depending on the version. In addition to the nominal voltage, pay attention to power rating, current draw, ECE approval, light colour, connector type, mounting points and the housing's protection rating. An LED unit is not automatically interchangeable with a halogen version: control via the BCM, SAM module or lighting control unit may monitor the bulb and trigger a fault message in the event of a different load.

Common fault symptoms include a completely failed fog light, moisture or condensation behind the lens, a cracked lens, a discoloured reflector, irregular light output or a dashboard warning indicating a lamp fault. On halogen versions, blown filaments, overheated bulb holders and oxidised contacts are typical causes. On LED units, internal moisture ingress, defective driver electronics or thermal overload often require complete replacement, as the light source and electronics are generally not repairable separately.

First check the fuse, relay or electronic output of the lighting module. Then use a multimeter to measure the supply voltage directly at the connector while the fog light is switched on. In a 24 V system, the voltage should remain virtually equal to the battery voltage under load; a significant voltage drop indicates contact resistance in the wiring harnesses, earth points or connectors. Also check the earth connection by measuring the voltage drop between the lamp earth and battery negative: more than a few hundred millivolts under load requires inspection of the earth connection. Check connector pins for green corrosion, loose terminals due to vibration, heat damage and moisture ingress. Finally, read out fault codes from the body or lighting module and compare the current output status with the measured voltage.

Always replace damaged fog lights with a unit featuring identical approval, mounting fitment and electrical connection. Before installation, clean the mounting surface and check bumper brackets for cracks or deformation; incorrect fitment causes stress in the lens and an incorrect beam direction. Fit new sealing rings, the correct lamp caps and, where specified, corrosion protection on the connector seal. Do not touch the glass of halogen bulbs with bare fingers, as grease residue causes localised overheating and premature failure.

After installation, adjust both beam patterns against a level test screen or using a professional headlight tester according to the vehicle specification. In the event of stone damage or moisture issues, preferably also replace the damaged cover, connector housing or cable repair kit. Braem can provide technical support with chassis-number identification and the choice between halogen and LED versions.