Top Up Washer Fluid : Warning Message

Top Up Washer Fluid in a Mercedes-Benz – A Case Study on Diagnosing and Fixing the Washer Fluid Warning Message

Keeping your windshield washer fluid topped up is essential for maintaining visibility and safety while driving. However, some Mercedes-Benz owners encounter an issue where the “Top Up Washer Fluid” message persists even after refilling the washer reservoir. This article explores a real-world case study in a Mercedes-Benz E Class W213, where a persistent washer fluid warning led to a detailed troubleshooting process and repair. If you are facing a similar issue, this guide will help you understand potential causes and solutions.

Customer Complaint: Top Up Washer Fluid Message Won’t Disappear

A customer brought their Mercedes-Benz E Class W213 to the workshop with a complaint that the “Top Up Washer Fluid” message remained on the dashboard even after refilling the reservoir to the maximum level.

How Much Washer Fluid Does a Car Hold?

The capacity of a washer fluid reservoir varies depending on the vehicle model. In most Mercedes-Benz models, including the E Class W213, the washer fluid capacity ranges between 4 to 6 liters (1 to 1.5 gallons).
If you are unsure about your vehicle’s washer fluid capacity, check your owner’s manual or look for capacity markings on the reservoir.

Initial Inspection

1. Check Washer Fluid Level
   • The first step was to check the washer fluid reservoir and top it up to the max level.
   • Despite this, the “Top Up Washer Fluid” message still appeared on the dashboard.
2. Perform Short Test via Xentry Diagnostic Tool
   • A fault code related to the washer fluid level sensor was detected.
   • This indicated that the sensor might not be functioning properly.

In-Depth Diagnostic Process

After detecting the level sensor fault, the following steps were taken to pinpoint the issue:

Step 1: Inspecting the Washer Fluid Level Sensor and Wiring

• Accessing the Sensor Unit
  • The wheel well cover was removed to visually inspect the washer fluid level sensor and its wiring.
  • Both the sensor unit and wire condition appeared normal upon inspection.
• Testing Sensor Functionality
  • Following Xentry diagnostic guide tests, a jump cable was connected to the sensor socket to simulate a functioning sensor.
  • However, the message did not disappear, suggesting an issue beyond the sensor unit itself.
• Measuring Resistance
  • The resistance value of the sensor unit (R) was tested and found to be within the acceptable range, confirming that the sensor itself was not faulty.

Step 2: Checking the Wiring Continuity

• Using the wiring diagram, the sensor wiring was tested for continuity between the sensor and the control unit.
• No continuity was found, indicating that the wires were disconnected at some point.

Step 3: Locating the Wiring Break

• Since the sensor and control unit wiring lacked continuity, a visual inspection was conducted in hidden areas where wiring could be damaged.
• Upon further investigation, it was discovered that rodents had chewed through the sensor wiring for the second time in the same location.

Repair Process and Solution

1. Repairing the Damaged Wires
   • The damaged wires were repaired using proper soldering techniques and insulation to ensure long-term durability.
   • Protective wire sheathing was applied to prevent future rodent damage.
2. Cleaning the Affected Area
   • A cleaning agent was used to remove any residue or odor that might attract rodents again.
3. Verifying the Fix
   • After repairing the wires, the washer fluid level sensor was tested again.
   • This time, the “Top Up Washer Fluid” message disappeared, confirming that the issue was resolved.

Final Observations

After successfully fixing the “Top Up Washer Fluid” issue, a new problem was detected:

• The date and time were incorrect on the dashboard.
• Further diagnostics revealed fault codes related to GPS, WLAN, and Bluetooth systems.
• These additional issues were unrelated to the washer fluid problem but required attention.

Key Takeaways for DIY Troubleshooting

If your Mercedes-Benz E Class W213 displays the “Top Up Washer Fluid” message even after refilling the reservoir, follow these troubleshooting steps:

1. Check the Washer Fluid Level – Make sure the reservoir is properly filled.
2. Run a Diagnostic Scan – Use an OBD scanner or Xentry tool to check for fault codes.
3. Inspect the Sensor Unit – Look for signs of damage or corrosion on the level sensor.
4. Test the Sensor Resistance – Use a multimeter to verify if the sensor is functioning correctly.
5. Check Wiring Continuity – If the sensor is fine, check for disconnected or damaged wires.
6. Look for Rodent Damage – If wiring issues persist, inspect hidden areas where rodents may have chewed through the wires.
7. Repair and Protect Wires – If damaged, repair the wires and apply protective sheathing to prevent future issues.
8. Recheck the System – After repairs, clear fault codes and check if the warning message disappears.

Conclusion

Persistent “Top Up Washer Fluid” messages in a Mercedes-Benz E Class W213 are often caused by faulty level sensors, damaged wiring, or rodent-related issues. By following a systematic diagnostic approach, you can identify the root cause and perform the necessary repairs to restore the system’s functionality.