MECH RPT REGARDING REVERSE INSTALLATION OF COOLING FAN VALVE AFTER A TEST.

Narrative

AT THE START OF MY SHIFT I WAS INFORMED I WAS GOING TO BE PUT ON AN ACFT WHICH WAS OTS DUE TO A PRESSURIZATION PROB. SEVERAL MECHS HAD ALREADY WORKED ON THE ACFT IN WHICH THEY HAD REPAIRED SEVERAL DUCT LEAKS. MYSELF AND ANOTHER MECH WERE TO TAKE THE ACFT OUT ON AN ENG RUN USING ENG BLEEDS TO PRESSURIZE THE ACFT IN ORDER TO PERFORM A DELAY CHK PER MAINT MANUAL. IN THIS TEST THE FORWARD EQUIP COOLING FAN VALVE LOCATED UNDER E&E FLOOR WAS TO BE WRENCHED CLOSED. DUE TO THE POS OF THE VALVE; ONE HAS TO REMOVE THE VALVE IN ORDER TO GET TO THE NUT IN ORDER TO WRENCH IT SHUT. THIS WAS DONE BY MYSELF. THE VALVE WAS REINSTALLED IN THE ACFT SECURED SHUT. WE THEN TOOK THE ACFT OUT FOR THE TEST RUN. THE ACFT PASSED THE DELAY CHK BUT ONLY BY 3 SECONDS PER MAINT MANUAL. WHEN ACFT WAS RETURNED TO THE GATE. THE SUN HAD JUST GONE DOWN. I AGAIN REMOVED THE VALVE IN ORDER TO UNLOCK THE VALVE AND REINSTALLED IT BACK INTO THE ACFT. THERE WERE NO OTHER PRESSURE CHKS DONE UNTIL THE NEXT MORNING WHEN THE ACFT TOOK OFF (MAINT PAPER WORK DOESN'T REQUIRE ANY FURTHER CHKS). AT THE TIME I INSTALLED THE VALVE THE LAST TIME; I WAS SURE I HAD INSTALLED IT CORRECTLY. BUT SINCE NO ONE TOUCHED THE ACFT THAT NIGHT IT WOULD LOOK LIKE I HAD MISTAKENLY INSTALLED IT IN REVERSE FLOW. I WOULD SAY THAT THE ONLY COURSE WE COULD HAVE TAKEN TO MAKE SURE THIS WOULD NOT HAPPEN AGAIN WOULD BE TO REPRESSURIZE IT AGAIN AT THE GATE USING THE APU (WHICH WE COULD NOT DO; DUE TO A CRACKED APU DUCT) USING A PILLOW TO PLUG THE EQUIP COOLING VENT AND THEN REMOVE IT WHEN ACFT HAD REACHED APPROX 3 PSI (NOTE VALVE CLOSES AT 2.5 PSI). IF VALVE WAS WORKING CORRECTLY; IT WOULD SLAM SHUT.