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Home >> Jeep >> 2002 >> Grand Cherokee 2WD Laredo V8-4.7L >> Repair and Diagnosis >> Wiper and Washer Systems >> Description and Operation >> Rear Wipers & Washers >> Part 3 of 3

Part 3 of 3

Fig.7 Rear Wiper Arm:




REAR WIPER ARM
The rear wiper arm is the rigid member located between the rear wiper motor output shaft that protrudes from the outer liftgate panel near the base of the liftgate glass opening and the rear wiper blade. This wiper arm features an over-center hinge that allows easy access to the liftgate and lift-gate glass for cleaning. The wiper arm has a die cast metal pivot end. This pivot end has a hole in it with internal serrations and a plastic pivot cover is secured loosely to and pivots on the wiper arm hinge pin to conceal the wiper arm retaining nut. The wide end of a tapered, stamped steel channel is secured with a hinge pin to the pivot end of the wiper arm. One end of a long, rigid, stamped steel strap, with a small hole near its pivot end, is riveted and crimped within the narrow end of the stamped steel channel. The tip of the wiper blade end of this strap is bent back under itself to form a small hook. Concealed within the stamped steel channel, one end of a long spring is engaged with a wire hook on the underside of the die cast pivot end, while the other end of the spring is hooked through the small hole in the steel strap. A molded plastic wiper arm support is snapped onto the wiper arm strap where it exits the channel. The entire wiper arm has a satin black finish applied to all of its visible surfaces.

A wiper arm cannot be adjusted or repaired. If damaged or faulty the entire wiper arm unit must be replaced.

The rear wiper arm is designed to mechanically transmit the motion from the rear wiper motor output shaft to the rear wiper blade. The wiper arm must be properly indexed to the motor output shaft in order to maintain the proper wiper blade travel on the glass. The wiper arm support is designed to lift and support the rear wiper arm and blade off of the glass when the rear wiper blade is parked. This support and the park ramp on the liftgate outer panel below the glass also provide an alignment reference to ensure accurate rear wiper arm and blade installation. The hole with internal serrations in the wiper arm pivot end interlocks with the serrations on the outer circumference of the motor output shaft, allowing positive engagement and finite adjustment of this connection. A hex nut secures the wiper arm pivot end to the threads on the motor output shaft and the pivot cover hinges and snaps over this connection for a neat appearance. The spring-loaded wiper arm hinge controls the down-force applied through the tip of the wiper arm to the wiper blade on the glass. The hook formation on the tip of the wiper arm provides a cradle for securing and latching the wiper blade pivot block to the wiper arm.

REAR WIPER BLADE
The rear wiper blade is secured by an integral latching pivot block to the hook formation on the tip of the rear wiper arm, and rests off the glass near the base of the liftgate glass opening when the wiper is not in operation. The wiper blade consists of the following components:
- Superstructure - The superstructure includes a stamped steel bridge and plastic links with claw formations that grip the wiper blade element. Also included in this unit is the latching, molded plastic pivot block that secures the superstructure to the wiper arm. All of the metal components of the wiper blade have a satin black finish applied.
- Element - The wiper element or squeegee is the resilient rubber member of the wiper blade that contacts the glass.
- Flexor - The flexor is a rigid metal component running along the length of each side of the wiper element where it is gripped by the claws of the superstructure.

All Grand Cherokee models have a single 31.00 centimeter (12.20 inch) rear wiper blade with a non-replaceable rubber element (squeegee). The wiper blade cannot be adjusted or repaired. If faulty, worn, or damaged the entire wiper blade unit must be replaced.

The wiper blade is moved back and forth across the glass by the wiper arm when the wiper system is in operation. The wiper blade superstructure is the flexible frame that grips the wiper blade element and evenly distributes the force of the spring-loaded wiper arm along the length of the element. The combination of the wiper arm force and the flexibility of the superstructure makes the element conform to and maintain proper contact with the glass, even as the blade is moved over the varied curvature found across the glass surface. The wiper element flexor provides the claws of the blade superstructure with a rigid, yet flexible component on the element which can be gripped. The rubber element is designed to be stiff enough to maintain an even cleaning edge as it is drawn across the glass, but resilient enough to conform to the glass surface and flip from one cleaning edge to the other each time the wiper blade changes directions.

Fig.12 Rear Wiper Module:




REAR WIPER MODULE
The rear wiper module 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 module. A rubber gasket, a bezel, and a nut seal and secure the motor output shaft to the liftgate outer panel. A molded plastic nut cover snaps onto the bezel to conceal the nut and improve appearance. The rear wiper module consists of the following major components:
- Bracket - The rear wiper module bracket consists of a stamped steel mounting plate for the wiper motor that is secured with screws to the wiper motor and to the liftgate inner panel.
- Electronic Controls - The rear wiper module electronic controls include the rear wiper system electronic logic and rear wiper motor electronic controls. The electronic controls for the motor include an electronic speed control that speeds the wiper blade near the center of the glass, but slows the wiper blade during directional reversals at each end of the wipe pattern and during wiper blade off-the-glass parking for quieter operation.
- Motor - The permanent magnet rear wiper motor is secured with screws to the rear wiper module bracket. The wiper motor includes an integral transmission, and the motor output shaft.

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

The rear wiper module receives non-switched battery current through a fuse in the Junction Block (JB) and is grounded at all times. The rear wiper module operation is controlled by the vehicle operator through battery current signal inputs received by the rear wiper module electronic controls from the right multi-function switch on the steering column. The module also receives an external control input from the liftgate flip-up glass ajar switch circuit. The rear wiper module electronic control logic uses these inputs, its internal inputs, and its programming to provide continuous wipe, delay wipe, wipe-after-wash and off-the-glass wiper blade parking. The wiper blade cycling is controlled by the rear wiper module electronic controls, which control current flow to the wiper motor brushes. The 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.
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