504 
Aug 15/69  52-61-0 
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BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details. 

TROUBLE  PROBABLE CAUSE  ISOLATION PROCEDURE  REMEDY 
Tread lights fail to illuminate with tread light switch in AUTO position Standby actuator motor continues to run after extension with STANDBY power Lower ladder fails to unlock from upper ladder Carriage step fails to rise Carriage top step is unstable  Normal stair extend limit switch defective Standby stair extend limit switch or standby airstair relay is defective Upper ladder has not extended far enough to trip lower ladder uplock trigger Lower ladder lock faulty Defective carriage step actuating mechanism Mechanism is out of adjustment  Disconnect airstair connector D934 and check for continuity between pin 3 and pin 11 of plug P1. If open, switch is defective Disconnect airstair connector D934 and check continuity between pin 17 and pin Y1 of standby airstair relay. If open, relay is defective. If not open, switch is defective Upper ladder out of sequence with carriage Extend upper ladder to the unlock position. Check control rod length allows full opening of up-lock hook assembly Extend carriage until actuator arm contacts actuator. Check linkage of rod assembly Extend carriage until actuator arm contacts actuator. Check rod assemblies for proper alignment  Replace switch Replace relay or replace or adjust switch. Refer to  52-61-151 Adjustment/Test Resequence airstair assembly. Refer to 52-61-100 Forward airstair manual operation Adjust control rod. Refer to 52-61-191 Adjustment/Test Adjust carriage step actuating mechanism. Refer to 52-61-131 Adjustment/Test Realign and adjust. Refer to 52-61-131 Adjustment/Test 

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506 
52-61-0 Page 108  BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details.  Jun 20/84 

501 
Aug 01/96  BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details.  52-61-0 Page 109 

501 
52-61-0 Page 110  BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details.  Aug 15/79 

500 
Sep 20/81  BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details.  52-61-0 Page 110A 

500 
52-61-0 Page 110B  BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details.  Sep 20/81 

TROUBLE  PROBABLE CAUSE  ISOLATION PROCEDURE  REMEDY 
Airstair door does  Normal airstair retract  Disconnect airstair connector  Replace or adjust 
not close after  limit switch defective  D934 and check continuity  switch. Refer to 
airstair has  between pin 9 and pin 10 on  52-61-141 
retracted with  the plug P1. If open, switch is  Adjustment/Test 
NORMAL power  Normal door close limit switch defective Normal door close relay or normal door motor defective  defective Disconnect connector D4668P on junction box and check for 28-volt dc at pin 8 of the plug with airstair control in retract position. If voltage is not present, switch is defective Disconnect normal door motor connector D912 and check for 28-volt dc at pin 2. If voltage is not present, relay is defective. If voltage is present, motor is defective  Replace or adjust switch. Refer to 52-61-601 Adjustment/Test Replace either the relay or motor 
Airstair door  Normal door close limit  Disconnect connector D4668P  Replace either the 
closes, but motor  switch or door close relay  on junction box and check  relay or switch 
continues to run  defective  voltage is present at pin 8 of plug with airstair control switch in normal position. If voltage is present, switch is defective. If voltage not present relay is defective 
Airstair door does  Standby airstair retract  Disconnect airstair connector  Replace or adjust 
not close after  limit switch defective  D934 and check continuity  switch. Refer to 
airstair has  between pin 14 and pin 15 on  52-61-141 
retracted with  the plug P1. If open, switch is  Adjustment/Test 
STANDBY power  defective 

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TROUBLE  PROBABLE CAUSE  ISOLATION PROCEDURE  REMEDY 
Airstair door does not close after airstair has retracted with STANDBY power (cont.) Airstair door closes but standby motor continues to run  Standby door close limit switch defective Standby door close relay or standby door motor defective Standby door close limit switch or door close relay defective  Disconnect connector D4668P on junction box and check for 28-volt dc at pin 7 on D4668P with the airstair control switch in the standby retract position. If voltage is not present switch is defective Disconnect standby door motor connector D914 and check for 28-volt dc at pin 2 of plug P1. If voltage is not present, relay is defective. If voltage is present, motor is defective Disconnect connector D4668P on junction box and check that voltage is not present at pin 7 of D4668P. If voltage is present, switch is defective. If voltage not present, relay is defective  Replace or adjust switch. Refer to 52-61-601 Adjustment/Test Replace either the relay or motor Replace or adjust switch. Refer to  52-61-601 Adjustment/Test 
　
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