A seat belt tension sensor assembly is adapted to be secured to the seat belt assembly of a vehicle. The assembly includes a housing for a seat belt anchor adapted for movement relative to the housing into an overload position where a portion of the anchor is abutted against a portion of the housing to limit and arrest the movement of the anchor relative to the housing and transfer the load from the anchor to the housing and then to an interior structure of the vehicle. In one embodiment, the housing forms a collar and the anchor includes an interior wall defining an aperture through which the collar extends when the anchor is mounted to the housing. Movement of the anchor relative to the housing is limited as a result of the contact between the interior anchor wall and the collar.