Many Mercedes-Benz owners notice a faint whirring sound from the passenger footwell area and wonder about its origin. This subtle noise often comes from a small fan located within the dashboard, specifically the “Mercedes Dash”. This isn’t a malfunction, but rather a component of your vehicle’s Automatic Climate Control (ACC) system. This article will explain the function of this fan, how to locate it, and simple steps to check if it’s operating correctly.
This small motor-fan assembly plays a crucial role in regulating the temperature within your Mercedes cabin. Despite its size, typically only 2-3 inches, it’s responsible for drawing in a small volume of air from the passenger footwell area. This air is then directed towards a temperature sensor. This sensor provides feedback to the ACC system, allowing it to accurately gauge the cabin temperature and adjust the heating or cooling accordingly. Interestingly, this fan often operates continuously, regardless of whether the ACC is actively engaged. Therefore, if you’re concerned that this little motor has stopped working, you’re not alone, as many Mercedes owners share this curiosity.
Accessing this fan, located near the main ACC blower plenum, is achievable with a few steps. Typically, you can access it from the passenger footwell. Start by removing the screws – usually three vertical screws – that secure the knee bolster or change tray in place. Once these are removed, you’ll likely encounter a plastic faceplate or escutcheon within the passenger’s change tray. Carefully pop this out, often by lifting from the right side and pivoting on the left, to reveal additional screws. Removing these screws will further expose the area. It’s important to note that in models equipped with airbags, like the W126, the airbag is positioned well above this area, so it shouldn’t impede access.
In many cases, after removing the knee bolster and escutcheon, the small motor should become visible. If it’s still not accessible, you might need to remove the passenger side metal ACC plenum. This plenum is typically held in place by three bolts. The third bolt can sometimes be a bit tricky to reach, often requiring a socket wrench with an extension. Removing this plenum will fully expose the small motor in question.
However, a simpler and less invasive method to check the functionality of this “mercedes dash” fan is the tissue paper test. Due to the fan’s weak suction, a standard tissue paper test might be inconclusive. A more reliable approach involves accessing the temperature probe directly. Locate the overhead grill and light assembly, and carefully lift it out. Disconnect the plastic tubing connected to the temperature probe. Now, place a small piece of tissue paper over the opening of the plastic tube. If the tissue paper is drawn towards the tube and sticks, it indicates that the motor and fan are functioning. It’s important to understand that this system isn’t designed to create significant vacuum pressure, so a gentle suction is normal.
In conclusion, the small fan in your “mercedes dash” passenger footwell is a vital part of your ACC system, ensuring accurate temperature regulation. By understanding its function and using the simple tissue paper test, you can easily verify its operation and address any concerns about your Mercedes climate control system. If you suspect a problem beyond a non-functioning fan, or if you are uncomfortable accessing these components yourself, consulting a Mercedes-Benz specialist is always recommended.
