Experiencing issues with your windshield wipers on a 1999 Mercedes E320 can be incredibly frustrating, especially when you’re caught in bad weather. One owner of a 1999 Mercedes E320 faced a perplexing problem where their windshield wipers stopped working and the turn signals malfunctioned, getting stuck signaling left. This guide will delve into the troubleshooting steps taken to diagnose this issue, offering insights and potential solutions for your Mercedes E320.
Initial Symptoms and First Steps
The problem began subtly, with the windshield wipers slowing down during rain before eventually failing completely. Simultaneously, the turn signals became erratic, persistently signaling left regardless of the desired direction. To tackle this, the owner embarked on a systematic diagnostic process, starting with basic checks:
1. Battery Check and Replacement
Ensuring proper voltage is crucial for any car’s electrical system. The first step was replacing the battery to eliminate it as a potential cause, especially since the old battery’s age was unknown. A healthy battery is fundamental for reliable operation of electrical components. However, in this case, a new battery didn’t resolve the windshield wiper and turn signal problems.
2. Fuse Inspection
Fuses are designed to protect electrical circuits from overloads. A thorough fuse check is essential when electrical issues arise. The owner meticulously inspected fuses in all relevant locations:
- SAM (Signal Acquisition and Actuation Module) fuses: These modules control various electrical functions.
- Driver’s side dashboard fuses: Another common location for important fuses.
- Fuses below the rear seat: Some Mercedes models have fuses in this location as well.
Each fuse was tested for continuity using a multimeter, a more reliable method than visual inspection alone. Despite this thorough check, all fuses were found to be in working order, ruling out a simple blown fuse as the culprit.
3. Grounding Point Examination
Proper grounding is vital for electrical circuits to function correctly. Poor grounding can lead to a range of electrical problems. The owner checked all grounding points within the car to ensure solid connections. Finding no issues with the grounds eliminated another common cause of electrical malfunctions.
4. SAM Module Diagnosis and Replacement
The SAM module is a critical component in modern Mercedes vehicles, controlling numerous electrical functions, including wipers and turn signals. A visual inspection of the SAM module revealed no obvious damage. To definitively rule out the SAM module, it was replaced with a known working unit from a similar 1999 Mercedes E320. This replacement, however, did not fix the non-functioning wipers and turn signals, indicating the problem lay elsewhere.
5. Turn Signal Switch Replacement
Given the initial turn signal issues, replacing the turn signal switch seemed like a logical step, especially since the original switch had been replaced before for a related problem. Despite installing a new turn signal switch, the problem persisted, suggesting the issue was not isolated to the switch itself.
6. EIS Module Investigation and Cloning
The Electronic Ignition Switch (EIS) module is integral to the Mercedes electrical system and interacts with both the turn signals and potentially the wipers via the SAM module. Suspecting the EIS due to unrelated SRS light and clicking noise issues, the owner replaced and cloned the EIS module. While the new EIS module resolved the SRS light and clicking noise problems, the windshield wipers and turn signals remained inoperative. It’s important to note that hazard lights and high beam lights were functioning correctly, which can sometimes help narrow down the problem area.
Suspecting CAN Bus Issues and Next Steps
After systematically eliminating several potential causes, the owner began to suspect a communication problem between the EIS module and the SAM module, possibly related to the CAN (Controller Area Network) bus. The CAN bus is a network that allows various electronic control units (ECUs) in a vehicle to communicate with each other. A fault in the CAN bus wiring or a module’s ability to communicate on the bus could explain the symptoms.
The owner’s next logical step was to investigate the wiring diagram between the EIS and SAM modules. However, tracing these wires proved challenging due to their complex routing throughout the vehicle.
The Need for Advanced Diagnostics
At this stage, without a clear wiring fault, the most effective next step is to utilize a professional-grade diagnostic tool like a Star Diagnostic system (specifically designed for Mercedes-Benz vehicles). This tool can:
- Read fault codes: Mercedes diagnostic systems store fault codes that can pinpoint the source of electrical problems.
- Test CAN bus communication: The tool can check if the EIS and SAM modules are communicating correctly on the CAN bus.
- Activate components: It may be possible to use the diagnostic tool to directly activate the windshield wipers and turn signals to further isolate the issue.
- Access wiring diagrams: Star Diagnostic systems often include detailed wiring diagrams, making tracing circuits easier.
While the owner expressed hesitation about investing in a Star Diagnostic tool due to the vehicle’s age and condition, it represents the most direct path to a solution at this advanced stage of troubleshooting. Independent Mercedes repair shops often have these tools and can provide professional diagnostic services.
Conclusion
Diagnosing electrical issues, especially those involving interconnected systems like windshield wipers and turn signals in a modern car like a 1999 Mercedes E320, can be complex. Systematic troubleshooting, starting with basic checks and progressing to more advanced diagnostics, is crucial. In this case, despite thorough component checks and replacements, the root cause likely lies within the vehicle’s communication network or related wiring. Utilizing a Mercedes-specific diagnostic tool is the recommended next step to accurately identify the fault and implement the necessary repairs. If you are facing similar issues, following these steps and seeking professional diagnostic assistance can help you resolve the “windshield wipers don’t work” problem on your 1999 Mercedes E320.
