Abstract: A card edge connector assembly with a housing with side walls and a housing base portion embodying an unique card edge auto thickness detection mechanism that includes a pair of movable block members with interconnected upstanding auto thickness detection members and contact pins, a pair of spring members positioned between the movable blocks and interior wall portions of the housing and a pair of stabilizing tie rod members cooperatively associated with the movable blocks for allowing translational movement, while preventing rotation. Each movable block having an extending projection slidably received within longitudinal channels formed in the base housing portion for maintaining the auto thickness detection mechanism in a selected position. Upon insertion of PCI cards between the contact pins and the auto thickness detection members, the contact pins and the auto thickness detection members are moved away from one another against the spring members for accommodating card edges of varying thicknesses.