What was found
PILOTS REPORTED THE LT BLEED AIR FLOW CONTROL UNIT WAS NOT FLOWING AT ALTITUDE. WITH THE RT FLOW CONTROL UNIT SELECTED OFF, THE CABIN ALTITUDE CLIMBED AT ABOUT 2,500 FPM. PERFORMED THE FLOW CONTROL UNIT TEST IN THE BEECHCRAFT 200 MM 21-10-00, PAGES 207 THROUGH 212. UNIT IN QUESTION FAILED THE CONTROL HEAD AND PNEUMOSTAT CHECK-OUT, HOWEVER, THE UNIT PASSED THE OTHER TESTS. AN EXCHANGE FLOW CONTROL UNIT AND PNEUMOSTAT WAS ORDERED AND INSTALLED. THE NEXT FLIGHT UNIT WAS CHECKED AND FUNCTIONED NORMALLY.