A B737-200 MADE 2 TKOFS AND DIVERTED BOTH TIMES DUE TO UNABLE TO PRESSURIZE THE CABIN CAUSED BY A FAILED AUTO PRESSURE CTLR.

Narrative

WHEN DEPARTING ZZZ JUN/MON/00; XA00 AM; USING A BLEEDS OFF TKOF; WE STARTED TO RUN THE AFTER TKOF CHKLIST AT 9200 FT MSL (3000 FT AGL). THE R SIDE BLEED WOULD NOT COME ON AND ALSO THE CABIN WOULD NOT PRESSURIZE. WE LEVELED OFF AT 10000 FT MSL; AND COMPLETED THE AUTO FAIL UNSCHEDULED PRESSURIZE CHANGE CHKLIST VIA THE QRH. ZZZ DEP CTL WAS TOLD AND WE REQUESTED TO COME BACK TO LAND AT ZZZ. OUR CABIN WAS NOW PRESSURIZED; BUT THE CABIN ALT WAS AT 9600 FT. THE OUTFLOW VALVE WAS CLOSED; BUT WE COULD NOT GET THE CABIN ALT TO COME DOWN WITH SINGLE PACK OPERATING. RETURN LNDG WAS UNEVENTFUL. ACR MAINT CTL CALLED OUT CONTRACT MAINT. THEY WORKED ON ACFT FOR 2 HRS UNDER MAINT CTL INSTRUCTIONS; VIA THE TELEPHONE. THEY RAN A PRESSURIZATION CHK ON THE MODE CTL PANEL AND DOOR SEALS. ALSO THEY DISABLED THE R BLEED VALVE THROUGH OUR MEL SYS. WE THEN DEPARTED ZZZ AT XC45 AM LCL AGAIN AND THE VERY SAME THING HAPPENED AS FIRST DEP AND RETURN. 4 HRS LATER 2 OF OUR MECHS ARRIVED FROM XXX. THEY INSTALLED A NEW PRESSURIZATION AUTO CTLR AND A R SIDE BLEED AIR VALVE. THEY TEST RAN ACFT AND IT OPS CHKED NORMAL. WE THEN FERRIED ACFT TO XXX ARRIVING AT XH15 LCL.