What was found
DURING CLIMB-OUT, CABIN ALT BEGAN TO CLIMB AT 1000 FT, BOTH PACKS APPEARED TO OP. NORMAL CABIN CLIMBED TO AN ALT OF 12,000 AND DESCENT BEGAN. POM PREC FOLLOWED STBY AND DC HAD NEG EFFECT TO CLOSE OUTFLOW FURTHER CARGO V. CLOSED LIGHT ILLUMINATED ENTIRE TIME ANOMALLY OCCURED. REPLACED PRESSURE CONTROLLER, REMOVED AND REPLACED RT PACK FWD VLV. PERFORMED TEST PER M/M. PRESS OF A/C TO CK FOR LEAKS. NO LEAKS NOTED A/C PRESSURIZATION GRD CKS NORMAL. PRESSURIZED A/C ALL INDICATION NORMAL.