The automatic car wash machine operates in sequence according to the preset program: the pre-wash solution first soaks and softens the dirt on the car body, then removes the stains through high-pressure water or a brush, rinses the residues with clean water, and finally, the fan blows away most of the accumulated water. If the chassis is still dirty and there are water marks on the car body after washing, the problem is often not just insufficient washing time, but rather a certain process failing to function properly.

The contactless model relies on a combination of chemicals and high-pressure water to complete cleaning, while the brush model adds physical friction. The overall process for both models is similar, with adjustments to the cleaning procedure based on specific needs. Some steps can be combined, repeated, or omitted.

Before the first spray: positioning and vehicle detection

The entire cleaning process begins with parking the vehicle in the designated location. In the station-style car wash, the driver parks the car, and the gantry or cleaning arm surrounds the vehicle to complete the cleaning process. In the tunnel-style conveyor belt car wash, the vehicles are sent to each cleaning station in turn by the conveyor chain. The two structures and the interaction with the vehicle body are different, but the basic cleaning principle remains the same.

Position sensors, wheel guides, signals, and control programs are used to synchronize the entire operation. Some equipment also scans the vehicle contour to automatically adjust the equipment movement trajectory and spray distance. Precise positioning is crucial, as any deviation of the vehicle will result in incomplete coverage of the preset spray range of the nozzle, significantly reducing the cleaning effect.

Before washing the car, the driver must follow the on-site instructions, close the windows, engage the gear, and apply the brakes. Loose body decorations, added roof accessories, or damaged original paint may make the vehicle unsuitable for the chosen washing mode.

Pre-soak loosens the dirt before removal

The dirt on the road is complex in composition, and vehicles often have floating dust, oily traffic film, insect corpses, salt deposits, and mineral precipitates adhering to them. Although clear water can wash away some loose dust, it is difficult to clean up the thin oil film that dries and darkens the paint of the vehicle solely with water.

Pre-soaking involves spraying cleaning agents on the vehicle body before the main wash. The surfactant can penetrate the paint surface, decompose and loosen oil and dirt, facilitating subsequent rinsing. Other ingredients in the formula can also mitigate the effects of hard water, disperse contaminants, and specifically target various types of deposits.

Alkaline agents are primarily used to remove oily traffic films and organic stains, while acidic agents are suitable for cleaning mineral scale. Many touchless car wash processes separately use alkaline and acidic agents, with the sequence of agent spraying and intermediate rinsing steps determined by the agent manufacturer and equipment program. Agents cannot be mixed or replaced arbitrarily, and mutual compatibility must be confirmed first.

Coverage and dwell time matter more than foam height

The chemical needs enough contact time to act, but it should not dry on the vehicle. Hot panels, direct sunlight, wind, and uneven application can shorten the useful dwell period. Heavy foam may look impressive, yet appearance alone does not establish cleaning strength or correct dilution.

A weak result can come from blocked applicators, incorrect metering, insufficient coverage, or a product poorly matched to the soil. Increasing concentration without checking those conditions can waste chemical and make rinsing harder. Operators should verify the delivered dilution against the product instructions rather than judge it by color or foam.

Some wash programs include a preliminary rinse to remove loose grit or cool the surface. Others apply pre-soak first. The correct sequence depends on the equipment and chemical program; a preliminary rinse is not a universal requirement.

The main wash: pressure

​A touchless machine uses directed water jets without brushes or cloth contacting the bodywork. Moving arms or gantries spray the roof, sides, front, and rear according to the programmed path. The wash depends heavily on chemical performance because it has no rubbing action to help remove persistent film.

Pressure alone does not determine the result. Nozzle condition, flow, spray angle, working distance, and coverage all affect how effectively the water reaches the surface. Raising pressure is not a sensible first response to missed areas, especially where damaged paint, seals, or loose trim may be vulnerable.

Recesses around badges, mirrors, and license plates can be harder to reach. A touchless wash may remove ordinary road soil well while leaving stubborn insect residue or strongly bonded contamination that needs a separate, suitable treatment.

Wheels, lower panels, and underbody areas

The areas between the wheels and the vehicle chassis require special attention during cleaning, as they are prone to accumulating brake dust, oil stains, dirt, and road salt. Depending on the equipment configuration and the chosen cleaning procedure, specialized nozzles and oscillating spray arms can be used to spray wheel hub cleaner or to rinse the chassis.

Ordinary pre-washing fluid for car bodies often struggles to fully remove stains from wheel hubs. Stubborn burnt stains and intricately designed wheel hubs may still retain dirt even after automatic cleaning. Furthermore, the surface coatings of wheel hubs vary, meaning that a higher concentration of cleaning solution does not necessarily equate to better cleaning results.

The chassis spray can remove visible dust and salt deposits, but it cannot penetrate deep into enclosed cavities or remove caked mud. Chassis spraying is only an auxiliary process for vehicle body cleaning, and it cannot replace manual deep cleaning in heavily soiled scenarios.

Optional protectants and the drying stage

Before the final drying process, some cleaning processes will be sprayed with drying additives, spray wax and other short-term protective agents. Different formulas can promote the aggregation of water into droplets, enhancing the gloss of the paint surface, but these types of automatic spraying products are not equivalent to long-lasting coatings for professional construction.

The compatibility and dosage of the medication are equally crucial. Excessive dosage or incomplete rinsing can easily result in drug residue and uneven distribution; If it remains on the glass, it will also form water marks, affecting the line of sight, not because the more medicine added, the better the effect.

The drying process mainly relies on high-speed fans to blow away moisture from the vehicle body. The nozzle angle, airflow intensity, vehicle parking position, and blowing duration all affect the drying effect. The body shape also has an impact: the rearview mirror shell, door handles, decorative strip gaps, and rear groove can easily hide water, and the vehicle will drip water after driving out.

A small amount of water droplets remaining in the rearview mirror position does not necessarily indicate a fan malfunction; But if there is a large area of water on the roof or hood, it is necessary to check the working condition, blowing coverage, and working hours of the fan. The drying effect is also affected by the previous process, and the incorrect ratio of residual cleaning agents or drying aids can change the state of moisture detachment from the vehicle body.

Some sites will be equipped with manual car cleaning or contact drying equipment. All materials in contact with the vehicle body must be kept clean and regularly maintained. The functions of towel wiping equipment and reusable towel drying device are different, and neither belongs to the standard automatic car washing process.

Summary

The above content is only for troubleshooting reference and cannot directly determine the cause of a single fault. For example, stubborn stains may have already penetrated the paint surface, and tar, gum, and particles embedded in the car paint often need to be treated separately in addition to regular automatic car washing.

When comparing different car washing systems, it is important to confirm the implementation methods of each process: whether the pre wash solution can fully cover the vehicle body, whether the chemicals can reach difficult to clean areas, which water source is used for final rinsing, and whether the fan can adapt to various vehicle body contours. The rich selection of medication options and value-added cleaning programs cannot compensate for the underlying problems such as spray dead corners, incorrect medication ratios, or poor rinse water quality.