A DORNIER 328 CLBING THROUGH FL180 HAD THE L AIR CONDITIONING PACK FAIL; R PACK PREVIOUSLY DEFERRED AS INOP; DSNDED TO 11000 FT DUE TO CABIN CLBING.

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I AM WRITING ABOUT A PRESSURIZATION PROB ON MAR/XA/00 ON THE FLT FROM DAY TO IAD. THE ACFT WAS XYZ AND WE BEGAN THE FLT WITH THE R ENVIRONMENTAL CTL SYS BLEED MEL'ED. AS WE WERE CLBING THROUGH APPROX FL180; WE NOTICED A BLUE ADVISORY MESSAGE 'L AND R PACK INOP' AND THAT THE CABIN ALT WAS CLBING AT A GREATER RATE THAN NORMAL. WE STOPPED OUR CLB AND PULLED UP THE ENVIRONMENTAL CTL SYS PAGE WHICH INDICATED THAT OUR ONLY BLEED HAD CLOSED. I INFORMED ATC OF THE PROB AND REQUESTED A LOWER ALT; IN WHICH THEY GAVE US 11000 FT. SHORTLY THEREAFTER; WE GOT AN AMBER 'L PACK FAIL' CAS MESSAGE AND AN OVERHEAT CONDITION WAS ON THE ENVIRONMENTAL CTL SYS PAGE. ALTHOUGH THE QRH DIDN'T DIRECTLY ADDRESS THIS PROB WHILE OPERATING ON 1 BLEED SOURCE; WE FOLLOWED IT AS CLOSELY AS POSSIBLE AND THE ENVIRONMENTAL CTL SYS BEGAN WORKING AGAIN. EVEN THOUGH THE PRESSURIZATION PROB WAS RESOLVED; WE CALLED MAINT AND DISPATCH TO INFORM THEM. DISPATCH CONFIRMED THAT OUR FUEL WAS SUFFICIENT TO CONTINUE TO IAD AT 11000 FT. IN ADDITION; MAINT WANTED US TO RECYCLE THE L HX FAN ON THE GND IN IAD. UPON ARR IN IAD; I CALLED MAINT ON THE TELEPHONE TO TOUCH BASE AND TO LET THEM KNOW THAT EVERYTHING WAS OPERATING NORMALLY. AFTER THE INITIAL PROB; WE NEVER EXPERIENCED ANYMORE ABNORMALITIES WITH THE ENVIRONMENTAL CTL SYS. WE FLEW THE ACFT 3 MORE LEGS WITH NO FURTHER PROBS.