Rear window washer works, front windshield washer does not.

Rear Wiper/Washer System Components
The rear wiper/washer system consists of the following components:
• Rear wiper/washer switch
• Window wiper module-rear
• Window washer pump-rear
• RR WIPER 15A fuse
• RR WPRB 25A fuse
Rear Wiper/Washer System Operation
The rear wiper module controls rear wiper motor operation. Battery voltage supplied to the module is used to operate the wiper motor in all modes and to return the rear wiper arm to the park position after the ignition is turned off. Accessory voltage supplied to the rear wiper/washer switch is used to supply the rear window wiper and washer switch signal circuits. In wiper switch positions 1 and 2 the wiper switch signal circuit voltage level to the wiper motor module determines the wiper motor delay interval. The rear window washer pump supply voltage circuit is used to provide the operating voltage for the rear washer pump for as long as the rear washer switch is pressed. The rear window washer switch signal circuit is used as a wash signal to the rear wiper motor module to operate the wipers during the rear wash operation.


Did you replace the rear wiper module ?

Replacing parts just to replace them wont fix a bad wire or part. Better to use a voltmeter and ohn meter to check if your getting power to the wires. You may have a bad connection or bad switch on the column for the pumps. Without checking the circuits it will behard to tell what it is thats wrong. Find a wiring diagram and trace the wires and components.

There is a electric motor that pumps washer fluid . Located in the bottom of the washer fluid tank .
Wash Operation (Front and Rear Wipers)
The front and rear washer systems use the same windshield washer fluid pump. When either the front or rear wiper is in the washer position voltage will be supplied to one side of the windshield washer fluid pump (depending on whether it is front or rear), while the other side of the pump is grounded.
At this point, the windshield washer fluid pump sprays solvent onto the windshield. When the front or rear washer is activated, the BCM receives an input from the switch that is activated. The BCM will control the wipers while in the WASH mode. The BCM will control either the front wiper relay or the rear wiper relay to turn on the wipers. The windshield wipers operate at low speed for 3 swipes and returns to the park position.

When turning on the washers do you hear the motor run ? Have some one try it while you listen at the washer fluid tank ! These pump motors do go bad .
turn OFF the ignition.
Disconnect the harness electrical connector of the windshield washer fluid pump.
Connect a test lamp from the windshield washer pump control circuit to a good ground .
Turn ON the ignition, with the engine OFF.
Press the front washer switch.
Does the test lamp illuminate?
YES or NO !

You have 2 washer pumps on the washer bottle. You need to check to see if power is getting to the rear pump motor by using a test light. When you press the button, one of the 2 terminals should light up. If it does, the pump could be bad or it may have a bad connection. If there is no power, you may have a bad switch.

the front and rear washer use the same reservoir and the same pump. Volkswagen reverses the polarity to spin the pump in opposite directions depending on whether you want the front or the rear to spray.

I’m happy to assist further over the phone at https://www.6ya.com/expert/jeremy_d728a59f986299fa

The front and rear share the washer pump. So, it could be many things.

the pump motor likely is bad. get a used washer fluid reservoir at a pick n pull yourself or at car-part.com. page with * is lowest cost.

Pump and Reservoir, Windshield Washer Removal

1. Disconnect the battery ground cable (14301).
   
2. Raise and support the vehicle.
   
3. Remove the RH wheel (1007).
   
4. Remove the RH front fender splash shield (16103). Refer to Section 01-02 for the removal procedure.
   
5. Remove the windshield washer reservoir top bolt.
   
   
6. Disconnect the windshield washer reservoir fluid level sensor electrical connector.
   
7. Disconnect the rear window washer pump electrical connector from the rear window washer pump.
   
8. Disconnect the windshield washer pump electrical connector from the windshield washer pump (17664).
   
9. Place a suitable drain pan under the windshield washer reservoir (17618) and drain the washer fluid.
   
10. NOTE: The rear window washer hose end is color-coded, matching the connector on the rear window washer pump. Match the colors to ensure proper installation.
    
    Disconnect the washer hoses from the windshield washer pump and the rear window washer pump on the windshield washer reservoir.
    
    
11. Loosen the two windshield washer reservoir side bolts.
    
12. Remove the windshield washer reservoir by sliding it out of the side slots.
    
13. Remove the windshield washer pump.
    
    Installation

To install, reverse the removal procedure. Tighten the lug nuts (1012) to 98-118 Nm (72-87 lb-ft).

Rear washer may have it's own reservoir . Can you hear a pump humming when you activate the washer? Look in the under flooor compartment

Principles of Operation
Operation of the windshield wiper and washer is controlled by the front wiper/washer amplifier assembly. The front wiper/washer amplifier input comes from the multifunction switch by means of a voltage divider circuit. A constant voltage is applied to the multifunction switch by the front wiper/washer amplifier. When the multifunction switch is moved into the LO, HI, or intermittent position, the voltage is directed through a series of resistors. This results in various voltages being returned to the module for each switch position. The module then grounds the appropriate circuit, based on the voltage signal received back from the multifunction switch. This causes the wipers to run intermittently, or at the appropriate speed. Voltage is supplied to the wiper motor by the CJB fuse F46 (20A).
When the multifunction switch wash button is depressed, it bypasses all of the resistors returning a full voltage signal to the module. The module then grounds the appropriate circuits to operate the windshield washer pump for as long as the switch is depressed. The windshield wiper speed is dependent on the position of the windshield wiper/washer switch.
Voltage for the windshield washer pump is also provided by CJB fuse F46 (20A).
Operation of the rear wiper and washer is controlled by the rear wiper/washer switch.
Voltage is supplied to the rear window wiper motor by the fuse junction panel fuse F44 (10A).
The rear window wiper motor ground is made or broken by the rear wiper/washer switch. When the rear wiper/washer switch is moved into the WIPER position, it grounds the rear window wiper motor circuit, causing the rear window wiper motor to run once every 10-15 seconds.
Voltage to the rear washer pump motor is also supplied by the CJB fuse F44 (10A). The rear washer pump is directly controlled by the rear wiper/washer switch which makes or breaks the ground for the washer pump motor, depending upon its position.
If the vehicle is equipped with a movable liftgate glass, a liftgate glass switch is utilized to prevent rear window wiper operation when the liftgate glass is open. This same switch also causes the rear window wiper to drop down approximately three inches when the liftgate glass latch is released.
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• The wipers stay on continuously — rear wiper

• Circuit.
• Rear wiper/washer switch.

• GO to Pinpoint Test L .

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Measure the resistance between rear wiper/washer switch C288 pin 6, component side and rear wiper/washer switch C288 pin 2, component side.

• Is the resistance less than 5 ohms with the switch depressed, and greater than 10,000 ohms with it released?

Yes GO to L2 .
No INSTALL a new rear wiper/washer switch. TEST the system for normal operation.

Measure the resistance between rear wiper/washer switch C288 pin 6, circuit WB08 (BU/YE), harness side and ground.

• Is the resistance greater than 10,000 ohms?

Yes INSTALL a new rear wiper /washer switch. TEST the system for normal operation.
No REPAIR circuit WB08 (BU/YE). TEST the system for normal operation.

there is another small relay box just below the windshield washer reservoir about 11/2" wide x about 4" long the washer pump relay is in there