GM Service Manual Online
For 1990-2009 cars only

Windshield Wiper Motor

A 2-speed windshield wiper motor operates the pulse-type windshield wiper. The wiper switch on the multifunction lever controls the wiper motor.

In the HIGH mode, the windshield wiper motor operates at high speed without any delay after the end of a wipe cycle. When the motor operates at any other mode, the motor operates at low speed. The motor uses a variable time delay between wipe cycles in order to reduce the wipe frequency.

The solid state logic of the windshield wiper motor determines the variable delay. The variable delay is based on the input voltage in CKT 96 (BRN) from the wiper switch. Various resistors in the wiper switch divide the voltage seen by the windshield wiper motor's fixed internal resistance.

A higher switch resistance produces a lower input voltage at the motor. The solid state logic also contains logic that returns the wipers to the fully down position, after the windshield washer switch is placed in the OFF position.

Windshield Washer Pump Motor

The windshield washer pump motor sprays the windshields as the wipers are moving. Each wiper has a flexible hose and a nozzle that move with the wiper in order to apply the spray where the wiper is in its'motion.

The windshield wiper motor operates the pump motor in response to the actuation of the momentary contact WASH lever switch on the multifunction lever. When you actuate the WASH switch, the wiper motor operates the wipers at high speed. The wiper motor provides the operating voltage to the washer pump motor on CKT 228 (RED). When the WASH lever is held in place, the wipers and the windshield washer pump motor operate.

WIPER fuse 11 through CKT 143 (YEL) powers the windshield wiper motor and the windshield wiper/washer switch. CKT 150 (BLK) at ground G201 ground the windshield wiper motor and the windshield washer pump motor.

MIST Position

When you move the windshield washer/wiper switch to the momentary contact MIST position, the low-speed voltage is placed on CKT 96 (BRN) to the windshield wiper motor. This voltage is seen at the variable voltage input of the solid state logic. The logic produces voltage pulses at the output to the motor. Operating voltage is applied to the motor's low speed windings. The pulse duration is long enough for a complete wipe cycle.

At low speed, there is no noticeable delay between the pulses The wipers operate almost continuously. These pulses are fed to the motor for the length of time that the operator maintains the MIST position. When the operator releases the switch, the solid state logic completes the current wipe cycle, and stops the wipers.

Delay Positions

When you move the wiper switch from the OFF position in the other direction, a momentary wiper action occurs. The instant wipe contact closes as the switch moves towards the delay positions.

This contact applies a momentary low-speed voltage to the wiper motor in order to start the wipe cycle. This avoids an excessive delay in waiting for a delayed operation if you select one of the delay positions.

The remaining contacts on the wiper switch are maintained and do not require the operator to hold the switch in position. There are 5 delay positions, labeled from 1 to 5 as lines on the switch handle.

In the first delay position, the switch selects the highest resistance. This produces the lowest voltage on CKT 96 (BRN). The wiper motor operates with a significant delay between the wipes. Moving the switch through the other delay positions progressively selects decreased resistance in the switch and shorter delay times at the motor.

LOW Speed Position

This position produces the low-speed voltage at the motor. The wipers operate a low speed without significant delay between the wipes.

HIGH Speed Position

In the HIGH position, the wiper switch applys full voltage on CKT 92 (PPL) to the wiper motor. This voltage applies to the motor's high speed winding. The HIGH speed position also closes contacts in order to apply the low-speed voltage to the motor on CKT 96 (BRN). This voltage allows the solid state logic to complete the wipe cycle when the switch is in the OFF position. Without this, the wiper blades could stay in mid-wipe when the switch is in the OFF position. The solid state logic also applies voltage to the motor's low speed winding. This has no effect while the high speed winding is operating.

WASH Position

The WASH lever on the washer switch normally operates when the wiper switch in the OFF position. This applies a full battery voltage on CKT 96 (BRN) to the windshield wiper motor. This also provides voltage on CKT 92 (PPL) through a diode in the wiper switch contact set.

This combination of voltages causes the wipers to operate at high speed and the windshield washer pump motor to operate. When you release the washer switch, the pump stops. The wipers complete the wipe cycle. Two or 3 wipe cycles follow the release of the washer switch and the stopping of the washer spray.