23. Rain-X is incompatible with a common type of windshield washer fluid sensor
known as a “continuity prong washer sensor.” This sensor is frequently found in European- and
American-brand vehicles, such as Volkswagen, Audi, Mini Cooper, BMW, Mercedes Benz and
Chrysler.

24. The continuity prong washer sensor detects the presence of washer fluid by
passing an electrical charge between two metal prongs, which are visible in this picture of the
sensor:

25. Electricity is conducted between these prongs only when they are immersed in the
washer fluid. When the fluid level falls below the level of the prongs, an electrical charge does
not pass, and the sensor triggers a warning light on the dashboard indicating that washer fluid is
low.

26. The use of these four Rain-X windshield washer fluids inhibits a charge from
passing between the metal prongs even when liquid is present. In essence, Rain-X reacts with
and/or coats the sensor’s metal prongs with electrically insulating chemical compounds that
isolate the metal electrodes and render them inoperative. These chemical compounds likely
consist of silicon based polymers including polysiloxane, hydroxyl-terminated
polydimethylsiloxane, and/or derivative compounds. As a result, the sensor fails to detect
whether washer fluid is present. Because a charge does not pass, the sensor triggers the low fluid
warning light, which remains illuminated whether or not washer fluid is present.