CLB TO AN UNAUTHORIZED ALT DURING FERRY FLT.

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AFTER 2 ATTEMPTS TO COMPLETE THE SCHEDULED FLT SEGMENT WITH PAX (PRESSURIZATION PROBLEMS) AND MUCH MAINT; I WAS ASKED TO FERRY THE ACFT TO A LARGER MAINT FACILITY. I AGREED. I TALKED TO THE SENIOR DISPATCHER AT FLT CTL (COMPANY) AND TOLD HIM TO FILE ME AT 10000 FT TO BE LEGAL; AND IF THE SYS WOULD MAINTAIN A LOWER CABIN ALT; I WOULD TRY TO CLB HIGHER. MAINT HAD INFORMED ME THAT; AFTER THEY HAD FINISHED; THEY THOUGHT THE SYS WOULD WORK NORMALLY; AND TO TRY IT AT HIGHER ALTS ON THE TRIP. THE SYS WOULD MAINTAIN ABOUT 3 PSID AND THEY COULDN'T TEST IT ON THE GND ABOVE THAT. THE PROBLEM HAD PRESENTED ITSELF AT 7 PSID ON BOTH PREVIOUS ATTEMPTS AT FL280 CRUISE; BUT WOULD HOLD A 3 PSID STEADY. AT 7 PSID; THE CABIN CLBED AT 300 FT PER MIN SO WE KNEW IT WAS WORKING TO SOME EXTENT. ENRTE ON THE FERRY FLT AT 10000 FT; THE CABIN WAS AT SEA LEVEL; SO WE WENT UP IN STAGES; FINALLY ARRIVING AT FL240; WHERE THE CABIN WAS AT 5000 FT AND CLBING AT 100 FT PER MIN. I THEN DISCOVERED THAT THE DISPATCHER THAT SENT THE FLT RELEASE WAS NOT THE SHIFT SUPVR I HAD TALKED EXTENSIVELY ABOUT THE SITUATION WITH; AND HAD FILLED OUT THE RELEASE RESTRICTING US TO 10000 FT. I HAD BEEN UNDER THE IMPRESSION THAT WE WERE FILED AT 10000 FT BUT COULD CLB IF THE CABIN PRESSURE ALLOWED IT. I SHOULD HAVE INSISTED THAT THE PERSON I TALKED TO WAS THE SAME PERSON DOING THE PAPER WORK. ON ARR; I TALKED WITH THE DISPATCHER; AND HE HAD NOT BEEN INFORMED OF THE COMPLETE DETAILS AND HAD THOUGHT WE WOULD BE UNPRESSURIZED ON THE FLT. OTHER THAN GOING ABOVE THE STATED 10000 FT LIMIT; THE FLT WAS NORMAL. SUPPLEMENTAL INFO FROM ACN 203487: DISPATCHED BY OUR COMPANY FLT CTL FOR AN 'UNPRESSURIZED FLT FOR MAINT CONVENIENCE.' WE HAD A FLC OF 3 PLTS PLUS 4 FLT ATTENDANTS; NO REVENUE PAX. DURING CLBOUT TO 10000 FT; THE ACFT APPEARED TO PRESSURIZE NORMALLY. WE DISCUSSED AND ELECTED TO REQUEST STEP-TYPE CLBS TO 15000 FT; FL200; AND FINALLY; FL240 TO CHK OUT THE REPAIRS THAT HAD BEEN MADE. THE DISPATCHER'S RESPONSE TO OUR CLB TO FL240 (WHEN DISPATCHED TO 10000 FT) MADE US THINK PERHAPS WE HAD ERRED OR POSSIBLY VIOLATED A RULE BY CLBING TO FL240 IN THE FIRST PLACE. THE CAPT; SO; AND I AM JUST CONCERNED THAT OUR GOOD-FAITH ATTEMPT TO GIVE MAINT A THOROUGH; COMPLETE INFLT EVALUATION MIGHT HAVE RESULTED IN SOME SORT OF VIOLATION; EITHER OF COMPANY RULES OR FAR'S. AT THIS POINT; NOBODY HAS INDICATED THAT TO BE SO.