Mercedes-Benz W212 blind spot radar faults
Why does the W212 blind spot radar stop working or show a fault?
The most common cause is moisture. The radar housing seal or the glued cover does not withstand frost or salt water, so water and salt oxidise the internal parts. The fault is also often an oxidised connector or wiring harness, in which case the rear radars cannot communicate with the system.
How is a W212 blind spot radar fault repaired and how can it be prevented?
The repair is usually a new wiring harness or radar. The radar is in a plastic box at the edge of the rear bumper, and it can be replaced from below without removing the bumper when the car is raised. Weatherproof silicone can be added to the cover seam, and drain holes should be drilled in the housing so water does not stay inside.
Is the red triangle in the mirror of the W212 Blind Spot Assist normally on?
The triangle usually lights up when overtaking and goes out when the overtaken car is far enough behind. The system does not react to fixed obstacles at the roadside. If the triangle stays on with no car beside you, or a fault message appears, the radar or its wiring should be checked.