Wiper and Washer Systems: Description and Operation

WIPERS AND WASHERS
The windshield wiper/washer system consists of the following components:
- Windshield wiper blades
- Windshield wiper pivot arm
- Windshield wiper mounting arm and pivot shaft assembly
- Windshield wiper motor
- Smart junction box (SJB)
- Windshield wiper switch
- Windshield washer nozzle
- Windshield washer reservoir
- Windshield washer pump

Principles of Operation

High Speed Windshield Wipers
High speed operation is activated when the multifunction switch supplies a ground to the high speed inputs of the smart junction box (SJB). When the SJB receives ground from the multifunction switch, the SJB activates the run/park and high/low relays by grounding the relay coils. When the wiper run/park and wiper high/low relays are activated, the wiper run/park relay supplies voltage to the high speed output of the wiper high/low relay. The SJB continues to cycle the windshield wiper in high speed mode until the inputs from the multifunction switch are changed from the HIGH speed position.

Low Speed Windshield Wipers
Low speed operation is activated when the multifunction switch provides ground to the low speed inputs of the SJB. When low speed is requested, the SJB activates the windshield wiper run/park relay by grounding the relay coil. When the windshield wiper run/park relay is activated, it supplies voltage to the low speed output of the windshield wiper high/low relay. The SJB continues to cycle the windshield wiper in low speed mode until the inputs from the multifunction switch are changed from the LOW speed position.

Intermittent Speed Windshield Wipers
When the multifunction switch is set to one of the 5 interval (INT) mode positions, the SJB will ground the wiper run/park relay to activate the windshield wiper motor for one low speed sweep followed by a pause, which will last between 1 and 20 seconds, depending on the position of the multifunction switch. Each of the 5 intermittent wiper dwell times are activated when the corresponding multifunction switch position provides ground to the intermittent mode inputs of the SJB.

Washer System
The windshield washer is activated by the SJB, which grounds the windshield washer relay coil when the multifunction switch provides ground to the wash input of the SJB.

Smart Junction Box (SJB)
In addition to being an electrical distribution center for several vehicle systems, the SJB is a multifunction electronic module, with inputs and outputs for several electrical systems, including the windshield washer system.
During normal operation, the SJB constantly monitors the circuits of electronic systems it controls. If the SJB detects an open, a short to ground, or a short to power in the windshield wiper circuits, it will set a diagnostic trouble code (DTC). DTCs can be retrieved with a IDS or equivalent tester. SJB DTCs related to the windshield wiper system will not illuminate the malfunction indicator light.