Experiencing issues with your 2017 Mercedes GLA 250 multifunction steering wheel buttons can be frustrating, affecting everything from your audio controls to cruise control and even your horn. Before considering a full replacement, diagnosing the root cause is crucial. This guide provides a step-by-step approach to troubleshoot and address common problems with your steering wheel buttons and horn.
First, begin with the simplest checks which often resolve the issue without needing extensive repairs. A common culprit for non-functioning steering wheel buttons and horn is a blown fuse. Locate the engine compartment fuse box in your Mercedes GLA 250. Refer to your vehicle’s manual for the precise location if needed. Once located, check fuse #13. This 7.5 amp fuse (typically brown) specifically protects the steering wheel circuit board, which controls your multifunction buttons and horn. Inspect the fuse for any signs of damage or a broken filament. Replacing a blown fuse is a straightforward fix if this is the problem.
If replacing fuse #13 doesn’t restore function, or if your steering wheel buttons begin working but the horn remains inactive, the next step is to examine the horn system itself. In the same engine compartment fuse box, check fuses #31a and #31b. These fuses are dedicated to the left and right horns respectively. Again, verify these fuses are in good condition.
Beyond fuses, the horns themselves or their connections could be faulty. The horns in a Mercedes GLA 250 are located behind the iconic Mercedes star in the front grille. Accessing them is relatively easy. Gently turn the star counter-clockwise by gripping the triangular spokes on its black plastic base. This will detach the star, providing access to the horns and their connectors. Ensure the horn connectors are securely plugged in and free from corrosion.
To determine if the horns are functioning, you can perform a direct power test. Carefully disconnect one of the horn connectors and use a test light or by momentarily applying direct power from a 12V source (like a car battery) to the horn terminals. If the horn doesn’t sound with direct power, the horn itself is likely faulty and requires replacement. If the test light illuminates when connected to the horn plug (with the horn circuit theoretically active), but the horn doesn’t sound when connected in the car normally, the issue might be further upstream in the wiring or control system.
WARNING: Disconnect Battery Before Proceeding to Airbag and Circuit Board Checks
The following steps involve working with the steering wheel airbag system. It is imperative to disconnect the vehicle battery and wait for at least 10 minutes before proceeding. This prevents accidental airbag deployment and potential injury, as well as avoids triggering the airbag fault light which requires diagnostic tools to reset.
A less frequent but possible cause, especially in vehicles with a history of impacts, is damage to the steering wheel circuit board. To inspect this, you’ll need to carefully remove the steering wheel airbag. This should only be attempted if you are comfortable and competent with automotive electrical systems and airbag safety procedures. If in doubt, consult a professional.
After safely removing the airbag (refer to your GLA 250 service manual for specific airbag removal instructions), you’ll see a metal retaining plate and underneath it, a black ABS triangular plate. Carefully remove this triangular plate. It typically opens up at the rectangular end, often secured by small tabs that can be gently pried open with a flat blade screwdriver. Inside, examine the circuit board for any visible damage, particularly around the horn button contact pins. Check if these pins are broken or misaligned, preventing proper contact when the horn buttons are pressed.
If the circuit board appears intact, the next step is to test the horn buttons themselves using a multimeter. Set your multimeter to continuity test mode. With the battery still disconnected and airbag removed, probe the horn button contacts on the circuit board. Press the horn buttons and check for continuity. If there is no continuity when the buttons are pressed, the buttons themselves may be faulty or there’s an issue within the circuit board.
If all the previous checks are successful, and the steering wheel buttons and horn still malfunction, the final component to consider is the clock spring (also known as the contact reel or spiral cable). The clock spring is a rotary electrical connector that maintains electrical contact to the steering wheel components as the wheel turns. A faulty clock spring is a common cause of steering wheel button and horn failures. Replacing the clock spring is a more involved repair, often requiring steering wheel removal and careful alignment during installation. While DIY clock spring replacement is possible, it’s often recommended to seek professional assistance to ensure correct installation and airbag system functionality.
In conclusion, troubleshooting 2017 Mercedes GLA 250 multifunction steering wheel button and horn issues starts with simple fuse checks and progresses to component-level diagnosis. By systematically following these steps, you can often pinpoint the problem, whether it’s a blown fuse, faulty horn, circuit board issue, or a failing clock spring. Remember to prioritize safety, especially when working with the airbag system, and consult a qualified mechanic if you are uncomfortable with any of these procedures.
