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A hyd not on PR off fault msg. no. 22-21020 msg. no. 22-21021 A hyd/PR /PR snsr PR/ A hyd /PR snsr LATCHED: NO LATCHED: NO Possible Causes: . Low pressure in A system hydraulics during YDC BITE pressure reducer test . Pressure reducer bypass valve . Yaw damper coupler Troubleshooting: . Verify resistance from D295 socket 31 to ground is 60 ohms. . Verify wiring between D295 socket 31 and D7377 socket 1 at the pressure reducer bypass valve solenoid. . Verify connection to ground from D7377 socket 2 at the pressure reducer bypass valve solenoid. . Verify wiring at the pressure reducer bypass valve: D295 socket 51 and D737 socket 3 D295 socket 52 and D737 socket 2 . Verify connection to ground from D737 socket 1 at the pressure reducer bypass valve. . Inspect electrical connectors for bent or broken pins, contamination, or damage. . If problem persists, replace the pressure reducer bypass valve. . If problem persists, replace yaw damper coupler. Possible Causes: . Low pressure in A system hydraulics during YDC BITE pressure reducer test . Pressure reducer bypass valve . Yaw damper coupler Troubleshooting: . Verify resistance from D295 socket 31 to ground is 60 ohms. . Verify wiring between D295 socket 31 and D7377 socket 1 at the pressure reducer bypass valve solenoid. . Verify connection to ground from D7377 socket 2 at the pressure reducer bypass valve solenoid. . Verify wiring at the pressure reducer bypass valve : D295 socket 51 and D737 socket 3 D295 socket 52 and D737 socket 2 . Verify connection to ground from D737 socket 1 at the pressure reducer bypass valve. . Inspect electrical connectors for bent or broken pins, contamination, or damage. . If problem persists, replace the pressure reducer bypass valve. . If problem persists, replace yaw damper coupler.
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PR on msg. no. PR /PR LATCHED: Possible Causes:
fault 22-21022 snsr NO . Hydraulic pressure not reduced in A system hydraulics during YDC BITE pressure reducer test . Pressure reducer bypass valve . Yaw damper coupler Troubleshooting: . Verify that the rudder pressure reducer valve manual lever is in the normal position. . Verify resistance from D295 socket 31 to ground is 60 ohms. . Verify wiring between D295 socket 31 and D7377 socket 1 at the pressure reducer bypass valve solenoid. . Verify connection to ground from D7377 socket 2 at the pressure reducer bypass valve solenoid. . Verify wiring at the pressure reducer bypass valve : D295 socket 51 and D737 socket 3 D295 socket 52 and D737 socket 2 . Verify connection to ground from D737 socket 1 at the pressure reducer bypass valve. . Inspect electrical connectors for bent or broken pins, contamination, or damage. . If problem persists, replace the pressure reducer bypass valve. . If problem persists, replace yaw damper coupler.
prgm pin fault msg. no. 22-21023 prgm pin /YDC LATCHED: NO Possible Causes: . Program pins do not match aircraft type selected during YDC BITE program pin test. . Operator error . Aircraft wiring . Yaw damper coupler Troubleshooting: . Inspect D295 socket 17, D295 socket 53, and YDC electrical connector for bent or broken pins, contamination, or damage. . Verify D295 socket 17 and D295 socket 53 resistance to ground is consistent with aircraft wiring diagrams, summarized; 737 MODEL D295 - 53 D295 - 17 -100/200/200 ADV GROUND OPEN RIDE QUALITY -100/200/200 ADV OPEN OPEN . Perform the yaw damper coupler installation test, ref AMM12-12-01, page 401 step 4. . If problem persists, replace yaw damper coupler.
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A hyd lo msg. no. lamp/YDC LATCHED: Possible Causes:
on fault 22-21025 /wiring NO . Flt control A low pressure light did not illuminate during YDC BITE pressure reducer test . Operator error . Flt control A low pressure light inoperative . Yaw damper coupler Troubleshooting: . Verify that flt control A switch is in the ON position. . Verify that flt control A light illuminates, press to test. . Verify wiring between D295 socket 57 and flt control A low pressure light. . Inspect D295 socket 57 and YDC electrical connector for bent or broken pins, contamination, or damage. . Perform the yaw damper coupler installation test, ref AMM12-12-01, page 401 step 4. . If problem persists, replace yaw damper coupler.
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