Mercedes Blind Spot Assist Inoperative: Reasons and Fixes

The Mercedes blind spot assist inoperative note appears on the dashboard when the car fails to analyze the hidden corners. It can fail due to an electrical crisis or damaged sensors in the active lane.

Mercedes Blind Spot

This complete article highlights all the reasons behind this Mercedes Benz crisis and shows ways on how to repair it.

Why Does Your Mercedes Show Blind Spot Assist Inoperative?

Your Mercedes shows the blind spot assist inoperative message because of a blown fuse or other electrical problems. It can also happen if the radar sensor gets wet or dirty or the steering sensor gets damaged. Towing or driving close to other vehicles can also fail the safety system.

  • Blown Blindspot Assist Fuse

The most common and manageable problem causing the blind-spot notification is a blown fuse. All vehicles contain fuses for specific electrical units. Breakage of the fuse is not a bad sign because it blows to protect the more expensive components.

Causes of Blind Spot on a Car

The hidden spot detection fuse also breaks as a result of an electrical spike. You can confirm the problem once you figure out the Mercedes blind spot assist fuse location. It may present near the battery, under the dashboard, or in the trunk, depending on the Mercedes model. Thus you can confirm the location from the manual and observe the specific fuse. If it appears dark or broken into two parts, it needs a replacement.

  • Electrical Disconnection of the Assist Feature

If you have replaced the fuse and shortly after that it blows again, your car might have a problem with the electric connections. If only the fuse associated with the hidden spot detection system blows, you should inspect the wiring and power supply for the system.

You can diagnose the electrical fault yourself or hire a mechanic for a thorough car inspection. You can check the circuit board or the tiny components that make the control module. You might notice broken or corroded wires and terminals. Moreover, you should check the power supply because a bad alternator or battery can cause the notification.

  • Water Inside the Proximity Sensor

If you are facing the blind spot assist inoperative W212 issue, the proximity sensor might have water inside. You can suspect this problem if the sensor only stops working after rain. Sometimes it is also accompanied by turn signal failure and non-functioning wiper blades.


These parts are connected to the same circuit, so they fail alongside the blind-spot detector when their fuses blow due to water. You can detect this problem by checking for corrosion in the sensor or moisture and cracks in the sensor mounts.

Water enters the sensor due to the following reasons:

  • Broken sensor seals
  • Cracked housing around the sensor
  • Prolonged exposure to snow or rain
  • Heating and cooling of sensor leading to condensation


  • Driving Close To Other Vehicles or Signal Interference

Sometimes there is no major reason behind the failure of a blind-spot detector because it can happen if you are driving close to another vehicle. For instance, you may notice the message on your dashboard while driving behind a truck for some time.

It can also happen if you have been driving too close to lane dividers or barriers. The blind spot assist inoperative meaning is the detection of vehicles in the hidden spot. But when you drive while staying close to another car, the sensor fails to analyze the hidden spot and stops working.

Additionally, there might be interference from the signals produced by equipment (such as TV or radio) in another car. It leads to false alerts, intermittent signals, or loss of function.

  • Polluted or Blocked Blind Spot Radar Sensor

Like all sensors, the blind-spot vehicle detector fails to work if blocked by dirt or foreign particles. You can expect it if you have not cleaned your Mercedes in a long time.
The sensor may be blocked due to dirt, dust, mud, or debris from the road. The sensor may also fail due to smudges, water spots, or car wash residues. Regularly cleaning the sensor can prevent these problems.

  • Mercedes Wheels Not Aligned

The blind-spot detector message may appear if the wheels on your Mercedes lack alignment. Poor alignment sends false signals because the vehicle fails to detect the vehicles in the hidden spot.

The blind-spot detection system receives signals from many sensors. These include the steering and speed sensors. Both sensors function according to the wheel alignment, so a misaligned wheel will give incorrect readings.

  • Compromised Steering Angle Sensor

A steering position sensor has a prominent role in keeping the car stable. It is present in the steering column and tracks the direction and angle of the steering wheel. A compromised steering sensor can produce the blind-spot aid inactive message.

The sensor may fail due to multiple reasons, such as aging or wearing with time. It can also fail due to contamination or electrical failures. Moreover, a road accident or impact can damage the steering sensor.

You can detect a faulty steering sensor if your car shows any of these signs:

  • Off-center or tilted steering wheel while driving straight
  • Difficulty turning the Mercedes steering wheel
  • Warning indicators on the dashboard
  • Poor car stability


  • Outdated Hidden Spot Detection Software

An outdated hidden spot detection software can also produce a message on your dashboard. The software fails due to a bug or other technical issues. In this case, the system might work inconsistently or completely shut down.

  • Towing a Trailer on Mercedes

Do you get the alert only while towing a trailer? If yes, you should know that the blind-spot vehicle detector is not compatible with towing.

Apart from the false blind corner signals, the car might break frequently. You should know that the lane change assist is not designed for towing. Thus, you should inspect the hidden spots yourself while changing lanes.

How To Fix a Mercedes Showing Blind Spot Assist Inoperative?

You can fix a Mercedes showing the blind spot assist inoperative note by cleaning the cloudy sensors or replacing the shabby sensors. Additionally, you can repair the electrical damages or update the hidden spot detection software. You can also ensure that the blind corner assist system switch is on.

  • Switch on the Blind-Spot Detection System

Sometimes people fail to realize that the blind-spot detection system is off. It usually has a switch under the dashboard, and you might have turned it off unintentionally. Thus, the first step is to locate the switch and turn it back on. If it tackles the problem, you are good to go. Otherwise, move on to the next repairing steps.

  • Clean the Blocked Sensor and Repair Worn Connections

The first repair step is to locate the sensor. The Mercedes blind spot assist sensor location varies with each model and make, but usually, it is found on the rear bumper or side mirrors. Then clear out all obstructions, such as debris or snow. Remove them gently so you do not damage or scratch the sensor. You can also use a mild hair brush or a soft cloth.

Fix a Mercedes Showing Blind Spot

You can also use a solution or cleaning agent. You can find cleaning solutions specifically for the sensor in the market. For example, isopropyl alcohol can clean the sensor if you apply it on a soft pad or cloth.

Clean the surface in a circular motion but do not apply much pressure as it can leave scratches on the sensor’s surface. Afterward, use a dry gentle piece of cloth to absorb the moisture. Skipping the drying part may leave water marks on the sensor.

If you find worn connections, such as corroded or naked wires, ask a mechanic to fix or replace them. Lastly, test your car to know if the sensor works.

  • Replace the Blown Mercedes Fuse

Are you looking for an answer to how to turn on blind spot assist Mercedes? Well, you can hire a mechanic to replace a blown Mercedes fuse.

It usually fixes the blind-spot detection problem. If you have experience, you can save more than half the replacement cost by replacing the fuse yourself. The steps below will guide you through the process:

  • Turn off all electrical components, including the ignition.
  • Find the fuse box in the engine or passenger compartment. The location will vary according to the Mercedes model. Check the user manual to know the fuse box’s exact location.
  • Pinpoint the fuse that looks burnt or broken and remove it. Gently pull it out with a fuse puller or thin pliers.
  • Buy a new fuse that has the exact amperage rating as the original one. Insert it in the fuse holder and test the car.


  • Reset or Update the Blind-Spot Detection Software

If the system does not work due to malfunctioning software, Mercedes blind spot assist reset may rectify the problem. Otherwise, you can update the software to keep the Mercedes blind spot assist always on.

You can consult the dealership or any service center to check for updates. If there are new updates, book an appointment and connect the car to the diagnostic tool. You can test the blind-spot detection system after installation of the update.

  • Replace the Worn Blind-Spot Sensors

If nothing else works, only replacing the sensor will resolve the concern. Since it is a technical procedure, we recommend hiring a mechanic or taking the car to the dealership.
The Mercedes blind spot assist sensor replacement cost ranges from $500 to $1,000. The cost depends on the number of worn sensors, labor costs, and the Mercedes model.

Assist Inoperative Message

Can the Same Fix Be Applied to Mercedes Blind Spot Assist Inoperative?

When it comes to Mercedes Blind Spot Assist inoperative issues, applying the same fix turn signal malfunction might not always be effective. A specialized mechanic should diagnose the specific problem and propose an appropriate solution. It’s crucial to address such malfunctions promptly to ensure proper functionality and safety on the road.


Receiving the Mercedes blind spot assist inoperative message can be an alarming situation. Luckily, this article mentions all repair and causing factors.

Here is a brief summary to wrap up the article:

  • The system fails due to a blown fuse, moisture or dirt in the radar, defective sensors, or outdated software.
  • Driving near other vehicles or towing can also hinder the blind-spot detector functions.
  • Repair the system by cleaning and drying the sensors, updating the software, or replacing the worn blind corner sensors.

You can restore the safety active lane system by diagnosing and addressing these issues.

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