Wiper Motor: Description and Operation

Fig. 12 Rear Wiper Motor:

REAR WIPER MOTOR
The rear wiper motor is concealed within the liftgate, below the liftgate glass and behind the liftgate trim panel. The end of the motor output shaft that protrudes through the liftgate outer panel to drive the rear wiper arm and blade is the only visible component of the rear wiper motor. A rubber bezel and grommet is secured with a nut to the motor output shaft to seal and secure the unit to the liftgate outer panel, and a plastic nut cover snaps over the top of the bezel for a neat appearance. The rear wiper motor consists of the following major components:
- Bracket - The rear wiper motor bracket consists of a stamped steel mounting plate for the wiper motor that is secured with screws to the wiper motor housing, and through two rubber grommet-type insulators to the liftgate inner panel.
- Motor - The single-speed permanent magnet rear wiper motor is secured with screws to the rear wiper module bracket. The wiper motor includes an integral transmission, a motor output shaft, an automatic re-setting circuit breaker, and the rear wiper motor park switch.

The rear wiper motor cannot be adjusted or repaired. If any component of the motor is faulty or damaged, the entire rear wiper motor unit must be replaced. The motor output shaft bezel and grommet, nut, and nut cap are available for service replacement.

The rear wiper motor operation is controlled by the rear wiper relay, which controls battery current flow to the rear wiper motor brushes based upon control outputs from the Central Timer Module (CTM). The CTM uses internal programming, hard wired outputs from the rear wiper motor park switch, and electronic messages received over the Programmable Communications Interface (PCI) data bus network from the rear wiper and washer switches in the air conditioner-heater control to determine when to energize or de-energize the rear wiper relay. The rear wiper motor park switch is a single pole, single throw, momentary switch within the wiper motor that is mechanically actuated by the wiper motor transmission components. The park switch alternately closes and opens a path to ground for the rear wiper motor control circuit input to the CTM, depending upon the position of the rear wiper blade on the liftgate glass. This feature allows the CTM to monitor the number of rear wiper motor cycles, as well as to keep the rear wiper relay energized long enough for the motor to complete its current wipe cycle after the wiper system or the ignition has been turned OFF, and to park the wiper blade in the lowest portion of the wipe pattern. The rear wiper motor is grounded at all times through a take out with an eyelet terminal connector in the body wire harness that is secured by a nut to a ground stud located on the lower left D-pillar in the passenger compartment. The automatic resetting circuit breaker protects the motor from overloads. The rear wiper motor transmission converts the rotary output of the wiper motor to the back and forth wiping motion of the rear wiper arm and blade on the liftgate glass.