As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
(CAN) FLIGHT 1790 DEPARTED CALGARY EN ROUTE TO KAMLOOPS, AIRCRAFT WOULD NOT PRESSURIZE AND RETURNED TO CALGARY. MAINTENANCE COULD NOT DUPLICATE DEFECT IN HANGAR AND AIRCRAFT WAS TEST FLOWN. PROBLEM REOCCURRED AND RETURNED TO HANGAR WHERE CONTINUITY TEST REVEALED FAULTY SQUAT SWITCH. AS AIRCRAFT WARMED UP CONTINUITY ON SWITCH RECTIFIED. SWITCH WAS REPLACED AND TEST FLOWN SATISFACTORY.