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May 01/99 BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details. 22-12-01 Page 107
YDC/solenoid/wiring/power/ faults
YD sol low volt msg. no. 22-21011 FDE: YD disenga 28V/sol/ YDC/wire LATCHED: Note 3 TYPE: Note 2 Possible Causes: . Low 28 VDC voltage applied to yaw damper coupler . Yaw damper engage switch . Yaw damper coupler . Rudder power control unit actuator solenoid Troubleshooting: . Verify voltage to D295 socket 4 is between 22.0 and 29.5 volts DC with the yaw damper DC circuit breaker closed. . Verify resistance from D295 socket 14 to ground is less than 2.0 ohms with yaw damper engage switch in the OFF position. . Verify resistance from D295 socket 20 to ground is 60 ohms. . Verify wiring between D295 socket 20 and D291 socket 1 at the rudder power control unit actuator solenoid. . Verify connection to ground from D291 socket 2 at the rudder power control unit actuator solenoid. . Inspect electrical connectors for bent or broken pins, contamination, or damage. . If problem persists, replace yaw damper coupler. . If problem persists, replace the rudder power control unit actuator solenoid.
PR sol low volt msg. no. 22-21012 28V/sol/ YDC/wire LATCHED: Note 3 TYPE: Note 2 Possible Causes: . Low 28 VDC voltage applied to the yaw damper coupler . Pressure reducer bypass valve . Yaw damper coupler Troubleshooting: . Verify voltage to D295 socket 4 is between 22.0 and 29.5 volts DC with the yaw damper DC circuit breaker closed. . 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. . Inspect electrical connectors for bent or broken pins, contamination, or damage. . If problem persists, replace yaw damper coupler. . If problem persists, replace the pressure reducer bypass valve.
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22-12-01 May 01/99
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BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details.
EHSV faults
YD EHSV fault msg. no. 22-21013 FDE: YD disenga YD EHSV /wrg/YDC LATCHED: Note 3 TYPE: Note 2 Possible Causes: . Rudder power control unit transfer valve . Yaw damper coupler
Troubleshooting:
. Verify resistance between D295 socket 30 and D295 socket 32 is 2K ohms.
. Verify wiring between D295 and the rudder power control unit transfer valve: D295 socket 30 and D291 socket 8
D295 socket 32 and D291 socket 5
. Verify wiring between D291 socket 7 and D291 socket 6 at the rudder power control unit transfer valve.
. Inspect electrical connectors for bent or broken pins, contamination, or damage. . If problem persists, remove and replace rudder power control unit transfer valve. . If problem persists, replace yaw damper coupler.
26 VAC faults
YDC msg. no. FDE: LVDT/DAA/ LATCHED: TYPE: Note
26V AC 22-21014 YD disenga wrg/YDC Note 3 2
fault
Possible Causes:
.
Rudder power control unit position
transducer
.
Yaw damper coupler
Troubleshooting:
.
Verify resistance between D295 socket 9
and D295 socket 1 is 100 ohms.
.
Verify wiring between D295 socket 9 and D295 socket 10 at the rudder power control unit position transducer.
.
Verify connection to ground at D295
socket 1.
.
Verify connection to ground at D291 socket 9 at the rudder power control unit position transducer.
.
Inspect electrical connectors for bent or
broken pins, contamination, or damage.
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