What was found
CLIMBING THROUGH FL250 WE GOT DOOR PAX OPEN CAS. RAN QRH AND DIVERTED BACK TO DEPARTURE AIRPORT. NO ABNORMAL PRESSURIZATION INDICATIONS. DURING TROUBLESHOOTING OF THE MICROSWITCH, THE PLANE WAS PRESSURIZED AND THE UPPER FWD MICROSWITCH CONNECTOR WAS FOUND TO BE PINCHED BY A ZIP TIE. THE CONNECTOR WAS SUSCEPTIBLE TO DISCONNECTION DURING SYSTEM PRESSURIZATION OR AIRCRAFT VIBRATION. THE ZIP TIE WAS REMOVED AND REPOSITIONED TO ELIMINATE INTERFERENCE WITH THE CONNECTOR. AN OPERATIONAL CHECK WAS PERFORMED SATISFACTORILY, WITH NO FAULTS NOTED. IN REF TO EMB 505E AMM 52-71-20