What was found
PILOT SQUAWKED VAC INOP, VAN ANNUNCIATOR INOP, TROUBLESHOOTING REVEALED THAT THE VAC INOP SWITCH HAD FALLEN OFF THE VACUUM REGULATOR, REGULATOR WAS REMOVED AND INSPECTED, FOUND THE REGULATOR TO BE GLUED TOGETHER AT ALL FITTINGS, THE REASON THE INOP SWITCH IS NOT SUPPORTED AND THE VIBRATIONS WORKED IT FREE, NO TOOLING MARKS TO SHOW THAT THE SWITCH HAD EVER BEEN REPLACED, NO TRACES OF GLUE WERE ON THE FITTING ATTACHED TO THE SWITCH