PR solenoid faults
PR sol fault msg. no. 22-21004 PR sol /wrg/YDC LATCHED: Note 3 TYPE: Note 2 . Pos Causes: Pressure reducer bypass valve sible
. 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.
. Inspect electrical connectors for bent or broken pins, contamination, or damage.
. If problem persists, replace the pressure reducer bypass valve.
. If problem persists, replace the yaw damper coupler.
YD switch faults
YD sw
msg. no.
FDE:
YD sw
LATCHED:
TYPE: Note
fault 22-21005
YD disenga
/wrg/YDC
Note 3
2
Possible Causes:
.
Yaw damper engage switch
.
Yaw damper coupler
.
Autopilot accessory unit
Troubleshooting:
.
Verify resistance from D295 socket 14 to ground is less than 2.0 ohms with yaw damper engage switch in the OFF position.
.
Verify wiring between D295 socket 14, the yaw damper engage switch, and autopilot accessory unit.
.
Inspect electrical connectors for bent or
broken pins, contamination, or damage.
.
If problem persists, replace the yaw damper engage switch.
.
If problem persists, replace the yaw damper coupler.
.
If problem persists, replace the autopilot
accessory unit.
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May 01/99 BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details. 22-12-01 Page 105
Airplane configuration faults
APL type error msg. no. 22-21006 FDE: YD disenga APL/pgm pin/YDC LATDHED: YES TYPE: Note 2 Possible Causes: . Yaw damper coupler replacement . Aircraft wiring . Yaw damper coupler Troubleshooting: . This fault may be present when a yaw damper coupler is initially installed into an aircraft. Perform the yaw damper coupler installation test, ref AMM12-12-01, page 401 step 4. . If the problem persists, 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 the problem persists, replace yaw damper coupler.
28 VCD faults
YDC 28V DC high msg. no. 22-21007 FDE: YD disenga 28V src /wrg/YDC LATCHED: NO TYPE: Possible Causes: . Excessive 28 VDC voltage applied to yaw damper coupler . 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. . If problem persists, replace yaw damper coupler.
YDC 28V DC low msg. no. 22-21008 FDE: YD disenga CB/wire/ 28V src LATCHED: Note 3 TYPE: Note 2 Possible Causes: . Low or No 28 VDC voltage applied to the yaw damper coupler . Yaw damper coupler Troubleshooting: . Verify yaw damper DC circuit breaker is closed. . Verify voltage to D295 socket 4 is between 22.0 and 29.5 volts DC. . Inspect electrical connectors for bent or broken pins, contamination, or damage. . If problem persists, replace yaw damper coupler.
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22-12-01 May 01/00
Page 106
BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details.
YDC/solenoid/wiring faults
YD sol short msg. no. 22-21009 FDE: YD disenga YD sol /YDC/wrg LATCHED: Note 3 TYPE: Possible Causes: . Rudder power control unit actuator solenoid
. Yaw damper coupler
Troubleshooting:
. Verify resistance from D295 socket 20 to ground is 60 ohms.
. Verify wiring 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.
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