Grand Cherokee 2WD Limited V8-4.7L (2002)
Rain Sensor: Testing and Inspection
AUTOMATIC WIPER ONLY - FALSE WIPES
False wipes are unnecessary wipes that occur when the control knob of the right multi- function switch is in one of the five Auto sensitivity positions and
no rain or moisture is apparent within the wipe pattern on the windshield glass. Because this system is designed to operate whenever it detects moisture if
the switch is in one of the Auto sensitivity positions any road spray bug splatters or mist from passing cars or trucks may occasionally cause the wipers to
cycle. Also the system will perform an initialization wipe each time the ignition switch is turned to the On position while one of the Auto positions is still
selected. These are normal characteristics of this system and are not false wipes.
False wipes generally are the result of foreign material or flaws that interfere with the system optics. The optics for this system allow the Rain Sensor
Module (RSM) to precisely transmit several InfraRed (IR) light beams and precisely monitor the intensity of these beams on the outer surface of the
windshield glass to determine the presence of moisture. The sensitivity of this system is such that anything that distorts the focus or intensity of the IR
light beams or affects the ability of the photo diodes within the RSM to see and accurately measure these light beams can result in the RSM logic
misinterpreting the resulting input data as moisture on the windshield. The optics for this system include the lenses of the RSM the lenses of the RSM
bracket the adhesive layer that bonds the RSM bracket to the inside of the windshield and the windshield glass.
The following procedure should only be used if false wipe occurrences are frequent and persistent. Perform diagnosis of the front wiper system the right
multi-function switch and the RSM using a DRBIII scan tool and the appropriate diagnostic procedures before performing the following:
1. Remove the RSM trim cover. Confirm that the spring clips of the RSM are fully engaged in their slots on each outboard edge of the RSM bracket
on the inside of the windshield glass.
If OK go to Step 2. If not OK press the spring clips inward until they snap over the bracket and are fully engaged in their slots.
2. Remove the RSM from the RSM bracket. Inspect the RSM lenses and the RSM bracket lenses for contamination.
