Windshield wiper system

The windscreen wiper linkage converts the rotary motion of the wiper motor into a controlled back-and-forth movement of the wiper arms. This mechanism is essential for a clear view through the windscreen in rain, snow, road spray and salt. In MAN and Mercedes trucks, buses and vans, the assembly generally consists of a wiper motor with gearbox, crank arm, link rods, ball joints, wiper spindles and mounting brackets. On vehicles with a wide or strongly curved windscreen, such as MAN TGX, TGS, Lion’s City and Neoplan coaches or Mercedes Actros, Arocs, Citaro and Tourismo, sweep angles, rod lengths and spindle positions are highly vehicle-specific.

Windscreen wiper linkages vary according to cab design, windscreen width, number of wiper arms, mounting side, motor output and electrical control. For example, a mechanism for a MAN TGL or TGM is not necessarily interchangeable with that of a TGS, TGX or TG3. Mercedes systems also differ significantly between Atego, Axor, Actros, Antos, Econic, Sprinter, Vito and Citaro. Buses and coaches, including MAN Lion’s Coach, Lion’s Regio and Neoplan Cityliner or Skyliner, use longer wiper arms and more heavy-duty linkage assemblies due to the larger wiping area and higher aerodynamic loads.

The spindles rotate in plain bearings or bronze bushes in the frame or in separate spindle housings. Trouble-free operation requires sufficient radial clearance, correct axial retention and a watertight seal where the spindle passes through the front panel. Corrosion on the wiper spindle, moisture ingress or dried-out grease increases the turning torque. This overloads the link rods, plastic ball sockets and the gear transmission of the wiper motor. Parts must always be identified using the vehicle chassis number. Visual comparison or selection based solely on the model name is never sufficient, as connector pin assignments, linkage geometry, park position and mounting points may vary by version.

A common fault symptom is a wiper that moves slowly, remains in one position or only makes a limited sweep. First check the fuse, relay, earth connection, multifunction switch and supply voltage at the motor connector. Measure under load with a multimeter: a noticeable voltage drop between the battery, supply, earth and motor indicates contact resistance in the wiring harness, connector or earth point. If the electrical supply is correct, remove the wiper arms and assess the mechanical turning torque of each wiper spindle separately.

A seized spindle can be identified by rust formation, difficult rotation or lateral play in the bearing bush. Worn ball joints cause a clicking noise, irregular wiping movement or a wiper arm that no longer moves in synchronisation. Also check for cracks in the crank arm, worn mounting holes and detached retaining clips. Measure the radial play of the spindle with a dial indicator; noticeable movement when applying hand force often indicates a worn bearing bush. Also check that the wiper arm has not slipped on the tapered or splined spindle. Damaged splines can shift the park position, even if the motor and linkage are still functioning.

Replace the complete windscreen wiper linkage when multiple pivot points are seized, link rods are worn or the spindle housings are affected by corrosion. Replacing individual link rods or bearing bushes is only advisable when the remaining parts operate within tolerance and are available separately. Install the linkage in the specified motor park position; an incorrect base position results in wiper arms colliding, insufficient wiping coverage or damage to the edge of the windscreen. Tighten the nuts on the wiper spindles to the specified torque and do not use grease on tapered splines, as this promotes slipping.

After installation, test the intermittent setting, low and high speeds, windscreen washer function and automatic return to the park position. Ensure that the wiper blades do not touch each other, the window rubber seal or the A-pillar. A correctly fitting mechanism and technical support during installation help minimise downtime and repeated dismantling.