Module assembly with mounting integrity detection including deformable washer

A module is mounted to a object with a fastener and a special washer. The fastener engages the object through a mounting opening in mounting portion of a module case. The washer has a first portion extending obliquely outward and downward to be deformed between the fastener head and an electrically non-conducting surface of the mounting portion and thus increase a mounting force on the module with mounting advancement of the fastener. The washer has a second portion extending axially into the internal opening to contact an electrically conducting insert therein and thus create a series electrical circuit from the typically grounded object through the fastener, washer and insert to a detecting circuit, which verifies that the module is securely mounted with a predetermined mounting force.