Check the continuity between the terminal and the body with an ohmmeter.

Check the continuity between the terminal and the body when the fine wedge is pushed. If there is continuity enve when the fine wedgew is pushed, replace it.

However, if there is non continuity when a 50 Kpa (70 psi) vacuum is applied through the oil hole, the switch is operating properly. Check to see that air doesn't leak. If air leaks, the diaphragm is broken. Replace the switch.