THIS B727 ACR FLC LOST THEIR PRESSURIZATION WHILE TROUBLESHOOTING A TEMP REG PROB WITH THE AIR CONDITIONING AND PRESSURIZATION SYS. THE FLC RECOVERED NORMAL OP AND CONTINUED TO THEIR DEST AT A REDUCED ALT.

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INCIDENT STARTED WITH SO DECLARING SHE WAS UNABLE TO GET L MIX VALUE TO MOVE FROM FULL COLD. SEVERAL MINS LATER THE ALT (CABIN) WARNING HORN SOUNDED. I IMMEDIATELY DONNED MY OXYGEN MASK. I VERIFIED WITH THE CAPT THAT THE CABIN WAS CLBING AND THAT A DSCNT WAS REQUIRED. HE ADVISED ATC OF OUR PROB AND REQUESTED AN IMMEDIATE DSCNT. WE WERE CLRED INITIALLY TO 15000 FT MSL WITH SUBSEQUENT CLRNC TO 11500 FT MSL. I FLEW THE RAPID DSCNT PROFILE AND COMMUNICATED WITH ATC. THE CAPT WORKED THE EMER PROC WITH THE SO. HE ALSO BRIEFED FLT ATTENDANT AND COMMUNICATED WITH THE COMPANY. A SHORT TIME AFTER LEVELING AT 11500 FT; CABIN PRESSURIZATION WAS REGAINED. WE INITIALLY CLBED TO 15000 FT MSL. WHILE CONSIDERING A DIVERT FIELD. CABIN PRESSURIZATION APPEARED TO BE OPERATING NORMALLY AT THIS TIME SO WE CLBED TO FL230. CABIN PRESSURIZATION CONTINUED TO OPERATE NORMALLY SO WE REQUESTED A REDISPATCH AND CONTINUED TO MSP AT FL230. ON DSCNT INTO MSP; THE L PACK OVERHEAT LIGHT ILLUMINATED; BUT NO PRESSURIZATION PROBS WERE ENCOUNTERED.