Mercedes A Class rear washer switch operates front washers ...

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 ?

Sounds like a wiring problem:
1. One of the wires attached to a pin in the connector attached to the wiring at the motor (not on the motor) may be corroded or have come loose, making intermittent contact, or
2. One of the wires in the harness between the motor and the switch is crimped somewhere around the tailgate and is intermittently opening, or
3. A bad motor ground wire connection at the tailgate.

How do you know the BCM is at fault ? Did you hook up a factory or someother type professional scan tool an check for DTC'S - diagnostic trouble codes ? Did you view how these system work in factory sevice repair information ? Did you use a wiring diagram an DVOM - digital volt ohmmeter an test electrical circuits ?

The BCM has nothing to do with the memory seats .
Memory Seat System Components
The memory seat system consists of the following components:
• Power Seat Switch
• Seat Horizontal Motor
• Seat Front Vertical Motor
• Seat Rear Vertical Motor
• Seat Recliner Motor
• Driver Seat Module
• Memory Seat Switch
Memory Seat System Description
Battery voltage is supplied to the driver seat module through the power seat circuit breaker. The driver seat module supplies the seat adjuster switch assembly with a battery positive reference voltage. While the seat adjuster switches are in an inactive state the switch contacts are closed to the adjuster switch ground circuit. When a seat adjuster switch is pressed to an active state the switch contact is closed to the reference voltage circuit. Battery voltage on a switch signal circuit indicates to the driver seat module the switch status is active. Each seat adjuster motor is controlled by the driver seat module through 2 motor control circuits. While the seat adjuster motors are in an inactive state the motor control circuits are closed to ground circuit contacts within the driver seat module. The driver seat module operates the seat adjuster motors by switching one of a motor's control circuits to battery voltage. The seat adjuster motors are bidirectional and the direction of adjuster motor rotation is determined by which of the adjuster motor control circuits is switched to battery voltage while the other remains grounded.


Memory Set/Recall Operation
The driver seat adjuster motors are equipped with potentiometer type position sensors used by the driver seat module to determine the seat position. The position sensors are supplied with 5-volt reference and ground circuits from the driver seat module. The position sensor signal circuits are referenced from ground within the driver seat module. The signal circuit voltage levels monitored by the driver seat module range from 0.39 - 4.58 volts and are determined by the wiper locations on the resistors within the motor position sensors. The position sensor circuit voltage levels are used by the driver seat module to determine the seat position when storing or recalling memory position settings.
The memory recall switch assembly on the driver's door provides inputs to the driver door module. Battery voltage is supplied to the memory recall switch assembly from the driver door module. When a memory recall 1, 2, or EXIT switch is pressed, the switch contacts close the appropriate switch signal circuit to the battery voltage supply circuit within the memory recall switch assembly. When the driver door module receives active switch signals from the memory recall switch assembly, the appropriate commands are sent to the driver seat module using the Class 2 Serial Data circuit.
Memory seat recall operation is allowed only with the transmission selector lever in the PARK position while the ignition is on. The transmission selector lever position data is provided to the driver seat module by a message through the Class 2 Serial Data circuit.
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Rear Wiper/Washer System Components
The rear wiper/washer system consists of the following components:
• Rear window wiper motor
• Rear washer pump
• Rear wash relay
• Rear wiper/washer switch
• RR WIPER Circuit Breaker 15A / ENDGLASS REG Circuit Breaker 30A
• WASH 20A fuse
• Body control module (BCM)
• Liftgate control module (LGM) / End gate module (EGM)


Rear Wiper Operation (with LGM)
The rear window wiper/washer switch is an input to the BCM. The requested rear wiper mode is sent to the LGM by the BCM, as a message on the serial data circuit. The rear window wiper motor is controlled by the LGM. The switch power circuit to the rear wiper/washer switch is a 12-volt reference supplied by the BCM during ignition on, accessory or RAP power modes. The rear wiper/washer switch is composed from a series of resistors and the switch position is determined by the voltage of the rear wiper/washer switch signal circuit to the BCM. The rear wiper/washer switch has continuity at all times and the BCM expects a rear wiper/washer switch signal voltage in all switch positions including OFF. The rear wiper motor is supplied battery positive voltage and ground. The LGM controls rear wiper motor operation through the rear window motor speed signal circuit. The rear window motor speed signal circuit is supplied a battery positive reference voltage by the rear window wiper motor module and is pulse width modulated to ground by the LGM. The duty cycle of the pulse width modulation determines the rear wiper motor operating mode. The liftglass and liftgate ajar switches are inputs to the LGM and must be in an inactive state in order for rear wiper washer system operation to be enabled. When an ajar switch is active the LGM suspends wiper motor operation directly and sends the ajar switch status messages over the serial data circuit enabling the BCM to suspend washer pump operation.


Rear Wiper Operation (with EGM)
The rear window wiper/washer switch is an input to the BCM. The requested rear wiper mode is sent to the EGM by the BCM, as a message on the serial data circuit. The rear window wiper motor is controlled by the EGM. The switch power circuit to the rear wiper/washer switch is a 12-volt reference supplied by the BCM. The rear wiper/washer switch is composed from a series of resistors and the switch position is determined by the voltage of the rear wiper/washer switch signal circuit to the BCM. The rear wiper/washer switch has continuity at all times and the BCM expects a rear wiper/washer switch signal voltage in all switch positions including OFF. The rear wiper motor is supplied battery positive voltage and ground. The EGM controls rear wiper motor operation through the rear window motor speed signal circuit. The rear window motor speed signal circuit is supplied a battery positive reference voltage by the rear window wiper motor module and is pulse width modulated to ground by the EGM. The duty cycle of the pulse width modulation determines the rear wiper motor operating mode. The rear window motor park signal circuit provides position status of the rear wiper to the EGM.
The rear wiper and washer operation is allowed if the following conditions are true:
• Power mode is run or accessory.
• Lower left ajar switch is closed.
• Upper left ajar switch is closed.
• Upper right ajar switch is closed.
• Upper left dome switch is closed.
• The end gate window is fully closed.
• No end gate window express down, up, or down is requested.
• No gate swing open or drop open is requested.
If rear wiper/washer operation is attempted and the end gate window is open the driver information center (DIC) displays "Tailgate Glass Down". If the rear wiper is not in the park position and an attempt to open end gate window is done, the DIC displays "Rear Wiper Obstruction".


Your best bet , take it to a qualified repair shop because you have no idea how these systems work .

None < LGM - liftgate control module inside the lift gate does .
Rear Wiper/Washer System Components
The rear wiper/washer system consists of the following components:
• Rear window wiper motor
• Rear washer pump
• Rear wash relay
• Rear wiper/washer switch
• RR WIPER Circuit Breaker 15A / ENDGLASS REG Circuit Breaker 30A
• WASH 20A fuse
• Body control module (BCM)
• Liftgate control module (LGM) / End gate module (EGM)

Your best bet , take it to a qualified repair shop. You have no idea of the complexity of these system's . Communication network between modules etc..... Could have DTC'S diagnostic trouble code's stored in the liftgate control module . An auto parts stores can not read these codes .

Power Door Lock Operation
The power door lock switches are integral components of the DDM and PDM. The switches are two position normally open rocker switches. When placed in either the lock or unlock positions, the switches provide a direct input to the DDM or PDM. The DDM or PDM monitors these inputs and sends a Class 2 message indicating a change in the switch's respective position. Modules which activate the power door lock motors receive the Class 2 message and activate the motor in the appropriate direction to lock or unlock the vehicle's doors and liftgate. The modules which activate the power lock motors are:
• DDM (driver door lock actuator).
• PDM (passenger front door lock actuator).
• BCM (both rear door lock actuators).
• LGM (liftgate door lock actuator).
The DDM, PDM and LGM are directly connected to the respective door lock actuator through the door lock motor lock and unlock circuits. Once a door lock or unlock request has been received, the module will supply battery voltage to one side of the actuator and ground the other causing the doors to lock or unlock.

Did you check the fuse ? Do you hear the wiper motor running ? If the fuse is good you would need to test the electrical circuit for the wiper motor ,viewing a wiring diagram an then use a DVOM - digital volt ohmmeter to test
What body type is it ? Vin 6 or 3 could have a circuit breaker for power supply or fuse ,both are located in the rear fuse block .

Rear Wiper/Washer System Components
The rear wiper/washer system consists of the following components:
• Rear window wiper motor
• Rear window washer fluid pump
• Rear wash relay
• Rear window wiper/washer switch
• RR wiper 15A circuit breaker
• WASH 20A fuse
Rear Wiper/Washer System Controls
• Body control module (BCM)
• Liftgate control module (LGM)
• Rear wiper/washer switch

Here is how it is controlled

Rear Wiper/Washer System Operation
The rear window wiper/washer switch is an input to the BCM. The requested rear wiper mode is sent to the liftgate control module (LGM) by the BCM as a message on the serial data circuit, and the rear window wiper motor is controlled by the LGM. The switch power circuit to the rear wiper/washer switch is a 12-volt reference supplied by the BCM during ignition on, accessory or RAP power modes. The rear wiper/washer switch is a series of resistors and the switch position is determined by the voltage of the rear wiper/washer switch signal circuit to the BCM. The rear wiper/washer switch has continuity at all times and the BCM expects a rear wiper/washer switch signal voltage in all switch positions including OFF. The rear wiper motor is supplied battery positive voltage and ground. The LGM controls rear wiper motor operation through the rear wiper motor control circuit. The rear wiper motor control circuit is supplied a battery positive reference voltage by the rear wiper motor module and is pulse width modulated to ground by the LGM. The duty cycle of the pulse width modulation determines the rear wiper motor operating mode. The liftglass and liftgate ajar switches are inputs to the LGM and must be in an inactive state in order for rear wiper washer system operation to be enabled. When an ajar switch is active the LGM suspends wiper motor operation directly and sends the ajar switch status messages over the serial data circuit enabling the BCM to suspend washer pump operation. The rear window washer pump is controlled by the BCM through the rear washer relay. Battery positive voltage is supplied to the coil and switch sides of the rear washer relay. When the rear window wash request is active the BCM energizes the relay by grounding the relay coil through the rear washer relay control circuit. When the relay is energized battery positive voltage to the relay switch is supplied to the washer pump control circuit.

Your best bet mite be to have a qualified repair shop check for codes in the BCM or LGM
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DTC B1017 or B3970

The rear wiper motor is supplied battery positive voltage and ground. The liftgate control module controls rear wiper motor operation through the rear wiper motor control circuit. The rear wiper motor control circuit is supplied a battery positive reference voltage by the rear wiper motor module and is pulse width modulated to ground by the liftgate control module. The duty cycle of the pulse width modulation determines the rear wiper motor operating mode.

In the under hood fuse box , should have diagram inside the lid . Front wiper's or rear ? Front fuse # 36 - 25 amp. Plus Two relay's PCB hi and Wiper PCB relay . Wouldn't think this being fuse problem . Wiper switch , motor etc... The wiper's are control by a computer . BCM - body control module .

The windshield wiper/washer system consists of front and rear wipers. The front and rear wipers are operative when the vehicle is in accessory or run. The front wipers have 4 different modes: Mist, Intermittent, Low, and High. When the front wipers are in the intermittent mode, there are 5 delay modes to chose from, commanded by the windshield wiper washer switch through the body control module (BCM). The rear wipers has an only one mode.

If the fuse is bad , could have a short to ground or wiper motor pulling to much current (amps) . Fuse's don't just blow for no reason ! Could also have DTC'S - diagnostic trouble codes stored in the BCM .
DTC B3715
DTC B3873
DTC B3875
DTC B3922

DTC B3715 02: Front Wiper Relay Drive Circuit Short to Ground
The body control module (BCM) controls the wiper motor based on input from the windshield wiper washer switch. The BCM monitors the wiper washer switch through three separate signal circuits and a ground circuit. The windshield wiper switch high signal circuit is used to determine high speed wiper operation, the windshield wiper switch low signal is used to determine low speed, intermittent, and mist operation through the use of a resistor ladder, and windshield washer switch signal circuit is used to determine washer operation.
The BCM controls the windshield wiper motor through two output controls, controlling two different PCB relays which control the desired wiper speed, high or low.
DTC B3922 00: Front Wiper Function Select Circuit

The PCB relay's are non- servicable , replace fuse box . Soldered in Your best bet mit be to take it to a qualified repair shop .

There are something's involved that you are not aware of , or familiar with . Electronic control modules .
Rear Wiper/Washer System Controls
• Body control module (BCM)
• Liftgate control module (LGM)
• Rear wiper/washer switch
Do you know what a serial data network is ?
Rear Wiper/Washer System Operation
The rear window wiper/washer switch is an input to the BCM. The requested rear wiper mode is sent to the liftgate control module (LGM) by the BCM as a message on the serial data circuit, and the rear window wiper motor is controlled by the LGM. The switch power circuit to the rear wiper/washer switch is a 12-volt reference supplied by the BCM during ignition on, accessory or RAP power modes. The rear wiper/washer switch is a series of resistors and the switch position is determined by the voltage of the rear wiper/washer switch signal circuit to the BCM. The rear wiper/washer switch has continuity at all times and the BCM expects a rear wiper/washer switch signal voltage in all switch positions including OFF. The rear wiper motor is supplied battery positive voltage and ground. The LGM controls rear wiper motor operation through the rear wiper motor control circuit. The rear wiper motor control circuit is supplied a battery positive reference voltage by the rear wiper motor module and is pulse width modulated to ground by the LGM. The duty cycle of the pulse width modulation determines the rear wiper motor operating mode. The liftglass and liftgate ajar switches are inputs to the LGM and must be in an inactive state in order for rear wiper washer system operation to be enabled. When an ajar switch is active the LGM suspends wiper motor operation directly and sends the ajar switch status messages over the serial data circuit enabling the BCM to suspend washer pump operation. The rear window washer pump is controlled by the BCM through the rear washer relay. Battery positive voltage is supplied to the coil and switch sides of the rear washer relay. When the rear window wash request is active the BCM energizes the relay by grounding the relay coil through the rear washer relay control circuit. When the relay is energized battery positive voltage to the relay switch is supplied to the washer pump control circuit.

Your best bet , take it to a qualified repair shop and have it checked for DTC'S - diagnostic trouble codes .
DTC B1017 or B3970
The rear wiper motor is supplied battery positive voltage and ground. The liftgate control module controls rear wiper motor operation through the rear wiper motor control circuit. The rear wiper motor control circuit is supplied a battery positive reference voltage by the rear wiper motor module and is pulse width modulated to ground by the liftgate control module. The duty cycle of the pulse width modulation determines the rear wiper motor operating mode.
DTC B3799

2
Turn the ignition ON.
Operate the rear wiper switch through all the switch positions.
Does the rear window wiper operate normally?
--
YES - Go to Testing for Intermittent Conditions and Poor Connections in Wiring Systems
NO - Go to Step 3
3
Install a scan tool.
Display the liftgate control module data list.
Observe the following parameters while operating the respective switches. Refer to Scan Tool Data List for typical values.
• Liftgate Ajar Switch
• Liftglass Ajar Switch
Did the scan tool indicate the correct switch positions?
--
Go to Step 4
Go to Courtesy Lamps Inoperative in Lighting Systems
4
Observe the requested rear wiper parameter in LGM data list.
Operate the rear wiper switch through all the switch positions.
Does the scan tool indicate the correct requested rear wiper parameter in relation to the switch position?
--
Go to Step 5
Go to Step 6

Do the wipers work ? Fuse for wipers is same as washer pump .
Principles of Operation
The wiper motors receive inputs from the following:

• Multi-function switch
• Powertrain control module (PCM)
• Ignition switch
• Smart junction box (SJB)

The following components are integrated in the wiper motors:

• Windshield wiper motor module
• High/low speed relay
• Run/park relay
• Washer pump relay
• Park sense (Hall-effect sensor)

Washer System
The windshield washer and the rear window washer are activated by the internal wiper motor modules when it receives a ground from the multi-function switch between the washer inputs. Depending on the correct ground, the internal wiper motor modules activate either the windshield washer or rear window washer relays (internal) by grounding the respective relay coil. When either module is activated, it connects voltage to the washer pump while the deactivated module provides ground to the washer pump. In this manner, voltage polarity is reversible to achieve directional change of the washer pump and washer fluid.

• The washer pump is inoperative

• Circuitry
• Washer pump
• Multi-function switch
• Windshield wiper motor
• Rear window wiper motor

• Go To Pinpoint Test I .

Does your expedition have programmable/recall memory option for seats an mirrors ?
Driver Seat Module
The power driver seat and power exterior mirrors are controlled by the driver seat module (DSM) only when the vehicle is equipped with the programmable/recall memory option.
On the Expedition Limited, the power fold exterior mirror option is controlled by the DSM. Before running a self-test or retrieving codes, the power fold switch must be inactive for at least 30 seconds.
This is a complex vehicle , electronics , control modules an serial data communication networks. You mite be better off taking it to the dealer or some other repair shop . There could be DTC'S - diagnostic trouble codes stored in the SJB - body control module !
B1667 Mirror Driver Up/Down Motor Stalled Go To Pinpoint Test D . B1668 Mirror Driver Right/Left Motor Stalled Go To Pinpoint Test D . B1669 Mirror Passenger Up/Down Motor Stalled Go To Pinpoint Test D . B1670 Mirror Passenger Right/Left Motor Stalled Go To Pinpoint Test D . B1735 Mirror Driver Vertical Switch Circuit Short to Battery Go To Pinpoint Test D . B1739 Mirror Driver Horizontal Switch Circuit Short to Battery Go To Pinpoint Test D . B1743 Mirror Passenger Vertical Switch Circuit Short to Battery Go To Pinpoint Test D . B1747 Mirror Passenger Horizontal Switch Circuit Short to Battery Go To Pinpoint Test D . B2312 Mirror Horizontal Feedback Potentiometer Circuit Failure Go To Pinpoint Test D . B2314 Mirror Passenger Horizontal Feedback Potentiometer Circuit Short to Battery Go To Pinpoint Test D . B2316 Mirror Passenger Vertical Feedback Potentiometer Circuit Failure Go To Pinpoint Test D . B2318 Mirror Passenger Vertical Feedback Potentiometer Circuit Short to Battery Go To Pinpoint Test D . B2320 Mirror Driver Horizontal Feedback Potentiometer Circuit Failure Go To Pinpoint Test D . B2322 Mirror Driver Horizontal Feedback Potentiometer Circuit Short to Battery Go To Pinpoint Test D . Normal Operation During normal operation, when the front wiper wash is selected, the windshield wiper motor provides power to the washer pump through circuit CRW14 (BU/WH) and ground is provided to the washer pump through circuit CRW12 (GY/OG) and the rear wiper motor. If rear wiper wash is selected, the rear wiper motor provides power to the washer pump through circuit CRW12 (GY/OG) and ground is provided to the washer pump through circuit CRW14 (BU/WH) and the windshield wiper motor.

Possible Causes
• Multi-function switch
• Open in circuit CRW14 (BU/WH), CRW12 (GY/OG), CRW07 (GY/BN), CRW20 (GY/YE), SBB49 (RD) or GD149 (BK/GY)
• Short to ground in circuit CRW14 (BU/WH), CRW12 (GY/OG), CRW07 (GY/BN) or CRW20 (GY/YE)
• Washer pump
• Windshield wiper motor
• Rear wiper motor
  This is

front or rear? some have both.
all this is in the operator guide,
http://justgivemethedamnmanual.com/honda/honda-fit-owners-manual/

page 236
fuse 6 runs both washer motors.
cab box, marked FRONT WIPERS.
the wiper and washer use the same fuse(alldata.com)
so is good, if wipers work.
yes,
bad washer , bad hoses, check valves or switch or wires.

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.