Wiper/Washer System Description

WARNING: This page is about a different car, the 2004 Pontiac Grand Prix. However, it is still accessible from the selected car via links, so may be relevant.

The body control module (BCM) controls wiper motor low speed operation, washer pump and high speed operation. The windshield wiper/washer switch supplies a Low or Ground on the signal circuits to the BCM for windshield wiper/washer operation. When WASH, MIST, DELAY, LOW, or HIGH is detected, the BCM energizes the Wiper relay by suppling Low signal to the relay coil. This allows battery voltage from the WIPER fuse to flow through the relay switched input then through the contacts and out the relay switched output to the WIPER HI relay switched contacts. Since the WIPER HI relay switched contacts are normally closed to the low speed circuit of the windshield wiper motor, the motor will operate at low speed. For HI speed operation the BCM supplies the same Low signal to the Wiper relay control circuit and also supplies a Low signal to the Wiper HI relay control circuit. The Wiper HI relay's normally opened contacts are now in series with the current supplying Wiper relay contacts. The Wiper HI relay normally open contact at this point supply current to the wiper motors HI input.