High-beam headlamp

Driving lamps increase visibility range on unlit roads, company premises and international routes where standard dipped and main beams do not provide sufficient light output. For MAN and Mercedes trucks, buses and vans, these auxiliary lamps are available as halogen driving lamps and LED driving lamps, with round, rectangular or vehicle-specific housings. Correct selection must always be based on the chassis number. Visual comparison, lamp diameter or selection based solely on the model name is never sufficient: differences in bumper configuration, mounting brackets, wiring harnesses, voltage level, connector pin assignment and control systems can occur within the same vehicle series.

Driving lamps are fitted to, among others, MAN TGL, TGM, TGA, TGS, TGX, TG3 and TGE, as well as Mercedes Atego, Axor, Actros, Arocs, Econic, Sprinter and Vito. On buses, they may be found on MAN Lion’s City, Lion’s Coach and Intercity, Mercedes Citaro, Intouro and Tourismo, and Neoplan coaches such as Cityliner, Tourliner and Skyliner. Older F90-, F2000-, M2000-, SK-, LN- and Vario vehicles often have a simpler 24 V circuit, while more recent vehicles are frequently monitored via a central vehicle module, CAN bus or pulsed control system.

Before ordering, check whether you require a separate driving lamp, an integrated lamp unit, a lamp bracket, a protective cover or a complete set with wiring harness, relay and switch. Important parameters include the nominal voltage of 12 V or 24 V, power consumption, beam pattern, ECE approval, EMC classification according to ECE R10, and the water and dust resistance of the housing. LED versions generally require less current than halogen lamps, but may be sensitive to incorrect polarity, voltage spikes and fault messages caused by insufficient load. Therefore, do not use an arbitrary LED lamp as a replacement for a halogen unit without checking electrical compatibility.

Common fault symptoms include a completely non-functioning driving lamp, flickering caused by a poor earth connection, moisture behind the lens, a weak beam or repeatedly blown fuses. On vehicles with front-end damage, broken mounting tabs, bent brackets and incorrectly adjusted lamp units are also frequent issues. A cracked lens or damaged seal allows moisture to enter; oxidation in the connector, corrosion on the circuit board or deterioration of the reflector often follows quickly.

First check the battery voltage and charging voltage, as undervoltage affects light intensity. Then use a multimeter to measure the supply voltage at the connector while the driving lamps are switched on. In a 24 V system, the voltage drop across the positive and earth cables must remain limited; a clear voltage loss indicates oxidised cable terminals, a faulty relay, contact resistance in the fuse holder or a poor chassis connection. Do not measure the earth connection for continuity only, but also under load using a voltage drop test.

Next, check fuses, relays, connector locks and the wiring harness near the bumper, chassis pass-throughs and tilting cab areas. On CAN bus-controlled vehicles, fault memory analysis must also be carried out: an output disabled by the control unit due to overload may only supply voltage again after the fault code has been cleared or after the correct repair procedure has been followed.

Replace driving lamps in the event of internal condensation, burnt reflectors, damaged LED modules, loose lens connections or deformed housings. Wiring repairs are appropriate when the damage is local: use cables with the correct conductor cross-section, adhesive-lined crimp connections and seals resistant to water, road salt and vibration. Install wiring harnesses without tension, with sufficient slack and protection against chafing.

After installation, both light beams must be adjusted to the same height and symmetrically. Also check operation together with the main beams, relay and dashboard warning. Braem can assist with technical identification based on the chassis number and a suitable part for a reliable, compliant lighting system.