B737 CREW LOST CTL OF CABIN PRESSURIZATION DURING CLB.

Narrative

CLBING THROUGH THE UPPER 20'S I TURNED ON THE WX RADAR IN PREPARATION FOR TSTM AVOIDANCE AHEAD ON OUR RTE. THE WX DISPLAY ANNUNCIATION WAS DISPLAYED AND SOON ASSOCIATED WITH AN EQUIP COOLING PROB. THE EQUIP COOLING SUPPLY OFF LIGHT SUBSEQUENTLY ILLUMINATED. I INSTRUCTED THE FO TO RUN THE IRREGULAR PROC FOR THE EQUIP COOLING. WHILE HE WAS LOOKING THAT UP IN THE FLT MANUAL THE CABIN ALT HORN SOUNDED. THE CABIN WAS VERIFIED TO BE CLBING ABOVE 10000 FT AT A RATE JUST OVER 500 FPM AND THE OUTFLOW SHOWED FULL CLOSED. WE IMMEDIATELY DONNED OXYGEN AND ESTABLISHED COMS. THE CHKLIST FOR CABIN ALT WARNING WAS THEN PERFORMED. HAVING 2 PROBS AT ONCE WAS DISCONCERTING. OUT OF CONCERN THAT WE HAD A MORE SERIOUS YET UNIDENTED PROB; WHILE THE FO WORKED ON REGAINING CTL OF THE PRESSURIZATION; I TOLD ATC OF OUR SIT AND REQUESTED AN IMMEDIATE DSCNT. ATC CLRED US TO FL180 AND ASKED IF I WAS DECLARING AN EMER. TO ALLOW TIME TO RUN THE PROC I TOLD HIM TO STAND BY AND I'D TELL HIM SHORTLY. PASSING THROUGH THE MID 20'S THE CABIN RATE REVERSED; SO I ADVISED ATC THAT WE DID NOT NEED TO DECLARE AN EMER. WE DSNDED TO 10000 FT AND HELD IN THE VICINITY OF DFW; CHKED ON THE STATUS OF THE CABIN; CONSULTED WITH DISPATCH AND MAINT. DURING THIS; OUR JUMP SEATER; AN AIR TFC CTLR; INDICATED THAT HE HAD HEARD A CRACKLING NOISE ORIGINATING BEHIND THE FO'S CIRCUIT BREAKER PANEL JUST AS EVENTS BEGAN. BASED ON THIS RPT AND COMPOUND PROBS IT WAS DECIDED A LNDG AT DFW WAS PRUDENT. THE CABIN ALT DID NOT EXCEED 14000 FT DURING THIS EVENT AND PAX OXYGEN WAS NOT DEPLOYED. NO PROB WAS FOUND THAT WAS COMMON TO BOTH MALFUNCTIONS. THE EQUIP COOLING FAN WAS DEFERRED; A NEW PRESSURE CTLR INSTALLED; AND THE FLT DISPATCHED WITHOUT FURTHER EVENT.