AFTER TKOF FROM ONT; FLT CREW OF A320 RECEIVE ECAM WARNING OF PRESSURIZATION FAILURES. FOLLOW PROCS AND DIVERT TO ZZZ.

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WE AGREED TO AND WERE CLRED BY THE COMPANY TO OPERATE A TYPE II MAINT FERRY FLT TO XXX. DEP AND WX IN ONT: DEP ATIS WAS CALLING FOR WIND 040 DEGS AT 20 KTS GUSTING TO 34 KTS WITH 10 MI VISIBILITY. WE AGREED THERE WAS A MEDIUM PROBABILITY OF WINDSHEAR ON TKOF. WE BRIEFED AND ELECTED TO OPERATE ACCORDING TO THE FLT MANUAL PROCS WHICH CALLED FOR A FLAPS 2 DEG TOGA TKOF. WE ALSO BRIEFED A DELAYED ROTATION UNTIL THE MAX OF 20K PAST VR. 'ROTATE' WAS TO BE CALLED AT 141K. DURING THE DEP BRIEFING; WE FULLY DISCUSSED THE TERRAIN SURROUNDING THE ONT ARPT AND IF WE LOST AN ENG; WE'D ELECTED TO GO TO ZZZ. TWR CALLED DEP WIND 050 DEGS AT 25 KTS GUSTING TO 37 KTS. V1; VR; V2; ROTATE WERE ALL CALLED AS BRIEFED. THE FO ROTATED AND WE ACCELERATED AND CLBED RAPIDLY AS THE ACFT WAS VERY LIGHT (114000 LBS). BTWN 1500-2000 FT; WE HEARD 'BING' -- ECAM. JUST THEN; WE GOT THE HDOF TO DEP. THE ECAM READ 'VENT SKIN VALVE FAULT.' THE FO REMAINED THE PF. I CHKED IN WITH DEP AND TOLD THEM WE HAD A PRESSURIZATION PROB AND TO PLEASE KEEP US CLR OF TERRAIN. THE CTLR GAVE US A CLB TO 7000 FT. WE TOLD HIM WE NEEDED TO STAY BELOW 10000 FT ACCORDING TO THE PROC. THE PROC HAD US PUT FIRST THE BLOWER SWITCH IN OVERRIDE; THEN THE EXTRACT SWITCH IN OVERRIDE. DURING THIS TIME AND WHILE THE FO WAS CLBING AS INSTRUCTED BY ATC REGARDING TERRAIN AVOIDANCE; OUR EARS BEGAN TO POP. THE ACFT WAS OVER-PRESSURIZING. THE NEXT PROCEDURAL ITEM ON THE ECAM WAS CABIN MODE SELECT AUTO; OPEN THE OUTFLOW VALVE. OUR EARS WERE STILL POPPING AS I HAD MY FINGER ON THE SWITCH TO OPEN THE OUTFLOW VALVE. WHILE THIS WAS HAPPENING; WE GOT ANOTHER ECAM; 'BLOWER' AS A SUB CATEGORY OF THE INITIAL 'VENT' ECAM. SHORTLY THEREAFTER; WE GOT ANOTHER ECAM (NOT INDENTED) 'CABIN PRESSURE SAFETY VALVE.' THE SCHEMATIC CONFIRMED THE SAFETY VALVE HAD OPENED. MAX CABIN ALT SEEN WAS 8200 FT WHILE WE WERE AT APPROX 8000 FT MSL. AFTER CONFERRING WITH THE FO; WE ELECTED AS BRIEFED TO DIVERT TO ZZZ. AN EMER WAS DECLARED AND THE FO WAS FIRST GIVEN A FULL RTE CLRNC (INCLUDING VICTOR AIRWAYS) AND THEN VECTORS WHEN PROMPTED. FUEL ON BOARD WAS 3 HRS; SOULS ON BOARD = 2. I RECEIVED A PATCH THROUGH THE ONT OPS TO DISPATCH AND MAINT. I INFORMED DISPATCH OF OUR PROB AND INTENTION TO PROCEED TO ZZZ. I READ OFF THE ECAM. I RELAYED THE MAX CABIN ALT NOTED. WE INTERCEPTED THE RWY 25R ILS TO ZZZ. FO HAD ARPT VISUALLY FROM OVER ONT. APCH AND LNDG WERE NORMAL. AFTER BLOCK-IN; FO DISARMED ALL DOORS AS PER FERRY PROCS.