Direction indicator

Turn indicators are safety-critical signalling components for MAN trucks, buses and vans such as F2000, TGL, TGM, TGS, TGX, TG3 and TGE, and Mercedes-Benz Atego, Actros, Arocs, Axor, Sprinter, Vito, Citaro and Tourismo. Various versions are also used on MAN Lion’s City, Lion’s Coach and Neoplan Cityliner, Tourliner or Skyliner vehicles. Depending on the year of manufacture, vehicle body and type approval, turn indicators may be integrated at the front, rear, in the exterior mirrors, mudguards, headlamp units, rear light units or side markers.

There are separate indicators with incandescent bulbs, halogen bulbs or LED modules, as well as complete lamp units with lens, reflector, bulb holder, seal and integrated cable connector. LED turn indicators generally operate with an internal electronic driver and consume much less current than bulb versions. As a result, they cannot simply be interchanged: the vehicle control unit often monitors circuit load and may register a bulb failure warning, increased flash rate or fault code if the resistance differs.

The correct part must always be determined using the chassis number. Visual comparison, the model name alone or the shape of the lens are never sufficient. Pay particular attention to the OEM reference, connector pin assignment, number of pins, left- or right-hand fitment, ECE approval, 12 or 24 V supply voltage and any CAN bus monitoring.

A rapidly flashing warning light, a completely failed side, moisture inside the lamp unit or intermittent operation are the most common fault symptoms. On conventional versions, corroded bulb holders, burnt contact surfaces, loose socket pins and bulbs with an incorrect wattage rating are frequent causes. In LED units, faults are often caused by moisture ingress, a defective driver, cracked solder joints or broken wires directly behind the connector. Mudguard- and mirror-mounted turn indicators in particular are vulnerable to stone impact, branches, vehicle washes and vibration.

Start by reading out fault codes in the central body or lighting control unit. Then check the fuse, relay or electronic flasher function according to the vehicle wiring diagram. Use a multimeter to measure the supply voltage at the connector while activating the turn indicator: in a 24 V system, the pulsed voltage under load should closely follow the battery voltage. Next, measure the voltage drop between the earth pin and the chassis; more than approximately 0.2 V indicates a poor earth connection, oxidation or a damaged cable terminal. A test lamp with sufficient load helps detect broken wires that may remain unnoticed with a high-impedance multimeter.

Only replace a damaged lens or separate bulb holder if the reflector, seal and connector housing are technically sound. In the event of condensation, do not only replace the lamp: check the gasket, ventilation, mounting points and hairline cracks in the housing. An LED unit with internal electronics is generally not repairable in a durable manner and is best replaced as a complete unit. Use only connectors with the correct terminal fit, locking mechanism and sealing; universal crimp connections without strain relief will eventually cause contact resistance and faults.

After installation, check the flash rate, hazard warning lights, dashboard warning and visibility from the prescribed angle. Correctly selected turn indicators reduce inspection failures, safety risks and unplanned downtime. Thanks to technical support and a controlled range of parts, Braem can help ensure correct identification based on the chassis number.