What was found
FLT ALTITUDE KNOB ON PRESSURE PANEL SKIPS AROUND ON ALTITUDE SELECTION, . WHEN TRYING TO ADJUST ALTITUDE, THE VALUE WILL JUMP FWD AND BACKWARD. ACFT GROUNDED. ON INITIAL TROUBLESHOTING IAW FIM 21-31, TASK 801, EXISTING FAULTS SHOW 031. PERFORMED FIM 21-31, TASK 801 FOR CABIN PRESSURE CONTROLLER NR 2, NO FAULTS NOTED. PERFORMED A BITE TEST OF THE NR 1 CABIN PRESSURE CONTROLLER IAW FIM 21-31, TASK 801, NO FAULT NOTED.