Rain Sensor: Operation

WARNING: This page is about a different car, the 2006 Dodge Sprinter. However, it is still accessible from the selected car via links, so may be relevant.

The rain sensor operates on battery current and a clean ground received from the rain sensor control module. The rain sensor contains Infrared (IR) diodes that direct IR light beams at the windshield at an angle. When the windshield glass is dry, most of this IR light is reflected back to the sensor, which uses photocell receivers to measure the intensity of the light. When moisture accumulates on the windshield glass, much of the IR light is refracted away from the photocell receivers. This causes changes in the signal output of the rain sensor. The rain sensor control module monitors the signal output from the sensor and then controls the wiper motor speed and wipe intervals accordingly.

It is important to note that the default condition for the wiper system is automatic wipers Off; therefore, if no message is received from the rain sensor by the rain sensor control module, the automatic wipers will be disabled. If automatic wipers are disabled, normal low and high speed continuous wiper operation are unaffected. Also, due to the low voltage nature of the rain sensor signal and the impact that minor fluctuations in this signal strength can have on wiper operation, grounded shielding circuits are provided at the roof and control module connectors to control electrical induction into the sensor signal circuit.

The hard wired rain sensor circuits may be diagnosed using conventional diagnostic tools and methods. However, conventional diagnostic methods may not prove conclusive in the diagnosis of the internal circuitry or the optics of the rain sensor. Refer to the appropriate wiring information.