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Part 3 of 3

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.

REAR WIPER RELAY
The rear wiper relay is located in the Power Distribution Center (PDC) near the battery in the engine compartment. See the fuse and relay layout label affixed to the inside surface of the PDC cover for rear wiper relay identification and location. The rear wiper relay is a conventional International Standards Organization (ISO) micro relay. Relays conforming to the ISO specifications have common physical dimensions, current capacities, terminal patterns, and terminal functions. The relay is contained within a small, rectangular, molded plastic housing. The relay is connected to all of the required inputs and outputs through its PDC receptacle by five male spade-type terminals that extend from the bottom of the relay base. The ISO designation for each terminal is molded into the base adjacent to the terminal. The ISO terminal designations are as follows:
- 30 (Common Feed) - This terminal is connected to the movable contact point of the relay.
- 85 (Coil Ground) - This terminal is connected to the ground feed side of the relay control coil.
- 86 (Coil Battery) - This terminal is connected to the battery feed side of the relay control coil.
- 87 (Normally Open) - This terminal is connected to the normally open fixed contact point of the relay.
- 87A (Normally Closed) - This terminal is connected to the normally closed fixed contact point of the relay.

The rear wiper relay cannot be adjusted or repaired. If the relay is damaged or faulty, it must be replaced.

The rear wiper relay is an electromechanical switch that uses a low current input from the Central Timer Module (CTM) to control a high current output to the rear wiper motor. The movable common feed contact point is held against the fixed normally closed contact point by spring pressure. When the relay coil is energized, an electromagnetic field is produced by the coil windings. This electromagnetic field draws the movable relay contact point away from the fixed normally closed contact point, and holds it against the fixed normally open contact point. When the relay coil is de-energized, spring pressure returns the movable contact point back against the fixed normally closed contact point. A resistor or diode is connected in parallel with the relay coil in the relay, and helps to dissipate voltage spikes and electromagnetic interference that can be generated as the electromagnetic field of the relay coil collapses.
- The rear wiper relay terminals are connected to the vehicle electrical system through a connector receptacle in the Power Distribution Center (PDC). The inputs and outputs of the rear wiper relay include:
- The common feed terminal (30) is connected to the rear wiper motor through the rear wiper motor control circuit to the rear wiper motor. When the rear wiper relay is de-energized, the common feed terminal is connected to ground through a take out and eyelet terminal connector of the headlamp and dash wire harness that is secured by a nut to a ground stud located on the left front fender inner shield in the engine compartment near the battery. When the rear wiper relay is energized, the common feed terminal of the relay is connected to battery current from a fuse in the Power Distribution Center (PDC) through a fused B(+) circuit.
- The coil ground terminal (85) is connected to the relay control output of the CTM through the rear wiper relay control circuit. The CTM controls the ground path for this circuit internally to energize or de-energize the rear wiper relay based upon its programming, electronic wiper and washer switch state message inputs from the heater-air conditioner control, and a hard wired input from the rear wiper motor park switch.
- The coil battery terminal (86) is connected to battery current from a fuse in the PDC through a fused B(+) circuit at all times.
- The normally open terminal (87) is connected to battery current from a fuse in the PDC through a fused B(+) circuit at all times.
- The normally closed terminal (87A) is connected to ground through a take out and eyelet terminal connector of the headlamp and dash wire harness that is secured by a nut to a ground stud located on the left front fender inner shield in the engine compartment near the battery.

The rear wiper relay can be diagnosed using conventional diagnostic tools and methods.
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