Windscreen wash nozzle

A properly functioning windscreen washer system is essential for clear visibility through the windscreen of MAN and Mercedes trucks, buses and vans. The system delivers washer fluid to the spray nozzles at sufficient pressure, allowing dirt, salt deposits, insect residue and road film to be removed together with the windscreen wipers. During intensive use in distribution, construction transport, public transport and international haulage, a defective washer system can quickly result in insufficient visibility and an increased safety risk. Parts must always be identified using the chassis number. Visual comparison or selection based solely on the model name is never sufficient, as reservoir capacity, pump connector, hose routing, nozzle type and electrical control vary by version.

The washer system generally consists of a washer fluid reservoir, electric washer pumps, connecting grommets, non-return valves, plastic pipes, T-pieces, heated or non-heated spray nozzles and controls via the steering column switch or cab electronics. Some versions have separate pumps for the windscreen, rear window or headlamp cleaning. Larger vehicles may require longer pipe runs, larger reservoirs and multiple nozzles to cover the full width of the windscreen.

For MAN TGL, TGM, TGA, TGS, TGX and TG3, as well as for Mercedes Atego, Axor, Actros, Arocs, Econic and Antos, the configuration differs according to year of manufacture, cab version, left- or right-hand-drive configuration and any headlamp cleaning system. For MAN TGE and Mercedes Sprinter, Vito, Viano, V-Class and Citan, the body variant, rear window wiper and heated nozzles also play a role. On Citaro, Intouro, Tourismo and MAN Lion’s City buses or Neoplan coaches, pipe length, reservoir position and distribution to wide windscreens are particularly decisive in selecting the correct components.

An electric pump must provide sufficient flow rate and pressure to create an even spray pattern, without the jet ending up beneath the windscreen wipers or over the edge of the windscreen. Hoses must be resistant to alcohol-based washer fluid, temperature fluctuations and vibrations. Ageing PVC or rubber pipes can harden, crack or come loose from pump connections and spray nozzles. Heated nozzles also have an electrical connection and must function correctly both electrically and hydraulically.

A pump that can be heard running but does not deliver fluid often indicates an empty reservoir, frozen fluid, a blocked suction filter, a cracked suction hose or a loose pump seal. If fluid only comes out on one side, check for kinked pipes, blocked T-pieces, contaminated spray nozzles or a defective non-return valve. A delayed spray pattern after the vehicle has been stationary often indicates fluid draining back due to a leaking valve or porous connection.

Start the diagnosis with a visual inspection of the reservoir, filler neck, hoses and couplings for leaks. Then check the fluid level and frost protection with a refractometer. While operating the system, measure the supply voltage and earth connection at the pump connector using a multimeter. If voltage is present but the pump does not run, the pump should be replaced. If the pump does run, disconnect the delivery line and check fluid delivery into a collection container. Clean blocked spray nozzles only with low-pressure compressed air or suitable cleaning fluid; probing with steel can deform the nozzle opening and disrupt the spray pattern.

In the event of a leak, do not only replace the washer pump, but also assess the connecting grommet, hose connections and any non-return valves. A new pump fitted to a dried-out seal can cause fluid loss again. When replacing components, flush the reservoir if algae growth, limescale residue or sediment is present. Then fill it with washer fluid suitable for the expected ambient temperature; diluted summer products can freeze during winter operation and damage the reservoir, pump housing or pipes.

After installation, check the spray pattern with the windscreen wipers operating and inspect all connections for leaks under pressure. A correctly fitting part reduces installation stress on pipes and prevents premature failure. Fast availability of suitable cab parts also helps prevent vehicles with limited visibility from being unnecessarily taken out of service.