What was found
AIRCRAFT PRESSURIZATION INTERMITTENT. PRESSURIZATION WILL WORK WITH NO DEFECTS ON ONE FLIGHT; THE VERY NEXT FLIGHT, SYSTEM WOULD NOT WORK AT ALL. CLEANED OUTFLOW AND SAFETY VALVES; STILL INTERMITTENT. INSTALLED NEW SAFETY AND OUTFLOW SOLENOID VALVES (A AND B), INSTALLED OVERHAULED SAFETY VALVE, AND RIGGED LEFT MLG GROUND CONTACT SWITCH IAW MM. PERFORMED SEVERAL FUNCTIONAL CHECK FLIGHT, NO DEFECTS NOTED. (K)