Light Rain Sensor Module (LRSM) - Description

DESCRIPTION





The Light Rain Sensor Module (LRSM) (1) is the primary component of the automatic wiper system. In some vehicle applications the LRSM is also capable of performing an ambient light sensor function; and, therefore, is alternately referred to as the Light Sensor Module (LSM) or the Rain Sensor Module (RSM). The LRSM is located on the inside of the windshield just below and to the right of the inside rear view mirror mounting button. The LRSM is concealed from view within the vehicle interior by a molded plastic inside rear view mirror bracket trim cover that fits over the top of the LRSM housing and the LRSM mounting bracket, but the LRSM is visible through the windshield glass from the exterior of the vehicle.

The molded black plastic LRSM housing has an integral connector receptacle (2) at the top with provisions for up to four terminal pins. These terminal pins connect the LRSM to the vehicle electrical system through a dedicated take out and connector of the overhead wire harness that extends from above the headliner. Openings on the windshield side of the housing are fitted with four convex clear plastic lenses. A spring steel retaining strap (3) extends forward on each side of the housing to latch the LRSM to a molded black plastic mounting bracket, which is permanently bonded to the inside of the windshield glass.

Concealed and protected within the LRSM housing is the electronic circuitry of the module, which includes two Infrared (IR) diodes, two photocells, and a microprocessor. The LRSM is a Local Interface Network (LIN) slave and communicates over a single LIN bus circuit with the Body Control Module (BCM) (also known as the Common Body Controller/CBC). The BCM is a LIN master and a gateway to the Controller Area Network (CAN) data bus. The BCM controls the exchange of electronic messages back and forth between the LRSM and other electronic modules in the vehicle.

The LRSM cannot be adjusted or repaired. If ineffective or damaged, the entire module must be replaced. The LRSM mounting bracket is serviced only as a unit with the windshield glass.