Rain Drop Sensor

WARNING: This page is about a different car, the 2003 Lexus ES 300 and 2002 Lexus ES 300. However, it is still accessible from the selected car via links, so may be relevant.

NOTE: If the rain sensor tape has been peeled during a windshield glass replacement, make sure to affix a new rain sensor tape. Failure to do so will lead to a system malfunction.

When the wiper switch is in the AUTO position, this function uses a rain sensor that is mounted on the front windshield glass to detect the amount of rain drops and controls an optimal wiping timing accordingly. See Fig 1.

The rain sensor consists mainly of an LED (Light Emitting Diode) that emits infrared rays and a photo diode that receives those rays. See Fig 2. The detection method is based on the infrared rays that are reflected by the front windshield glass.

For example, if no rain drops are present in the detection area, the infrared rays emitted by the LED are all reflected from the windshield glass and are received by the photo diode. If rain drops are present in the detection area, a portion of the emitted infrared rays penetrates with the change of index of reflection outward of the windshield glass via the rain drops, thus reducing the amount of infrared rays that are received by the photo diode. The amount of this reduction is then used to detect the amount of rain drops. Thus, this function controls the INT, LO and HI operations in order to operate the wipers at an optimal wiping timing.

Fig 1: Identifying Rain Sensor System Diagram

Fig 2: Identifying Rain Sensor Detecting Method