521 
Oct 20/83  52-61-0 
Page 103 
BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details. 

526 
52-61-0 Page 104  BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details.  Aug 15/78 

TROUBLE  PROBABLE CAUSE  ISOLATION PROCEDURE  REMEDY 
Airstair will not  Door interlock relay  Disconnect connector  Replace relay or 
extend with  defective if airstair  D4822J at interior control  adjust door warning 
NORMAL power  extends with external control only Normal extend limit switch defective Normal door open switch defective Normal airstair relay or normal stair motor defective  panel and check for 28 volts dc at pin 5. If voltage is not present, relay is defective or forward entry door warning sensor is defective Disconnect airstair connector D934 and check continuity between pin 5 on plug P1 and pin Y1 on normal relay K1. If open is present, switch is defective Disconnect airstair connector D934 and check for 28 volts dc at pin 5 on D934 with airstair control in extend position. If voltage is not present, switch is defective Disconnect normal motor connector J4 and check for 115 volts ac at pins 1, 2 and 3 with airstair control in extend position. If voltage is not present at all three pins, relay is defective. If voltage is present, motor is defective  sensor. Refer to  52-71-0 Adjustment/Test Replace or adjust switch. Refer to  52-61-151, Adjustment/Test Replace or adjust switch. Refer to  52-61-611 Adjustment/Test Replace either the relay or motor 
Airstair will not  Door interlock relay  Disconnect connector D822J  Replace relay or 
extend with  defective if airstair  at interior control panel and  adjust door warning 
STANDBY power  extends with external control only  check for 28 volts dc at pin 2. If voltage is not present, relay is defective or forward entry door warning sensor is defective  sensor. Refer to  52-71-0 Adjustment/Test 

506 
Aug 15/68  52-61-0 
Page 105 
BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details. 

TROUBLE  PROBABLE CAUSE  ISOLATION PROCEDURE  REMEDY 
Airstair will not extend with STANDBY power (cont.) Airstair extends too slow with normal power  Standby door open limit switch defective Standby airstair relay or standby airstair motor defective Normal airstair relay, or normal airstair motor is defective Speed up switch or relay defective  Slow-down operating switch or slow-down operating relay defective  Disconnect airstair connector D934 and check for 28 volts dc at pin 17 on D934 with the airstair control in the standby extend position. If voltage is not present, switch is defective Operate airstair in standby mode. If stair operates, motor and relay ok. If stair does not operate, see following trouble for remedy: Open FORWARD AIRSTAIR STANDBY CONTROL circuit breaker and operate airstair in normal mode. If stair extends, relay and motor ok. If not, motor or relay is defective. See proceeding trouble for remedy With airstair retracted and FORWARD AIRSTAIR ACTUATOR circuit breakers open, check for 28 volts dc at terminals X1 and A2 of speedup relay with control in extend position. If both voltages are present, relay is defective. If both are not present, switch is defective. Extend airstair fully, using normal power and note ladder rotation rate. If rate is too rapid, slow-down switch or relay is defective  Replace or adjust switch. Refer to  52-61-611, Adjustment/Test Replace or adjust speedup switch. Refer to 52-61-211. Replace relaySee following trouble for rapid airstair ladder extension 

526 
52-61-0  Aug 15/69 
Page 106 
BOEING PROPRIETARY - Copyright . - Unpublished Work - See title page for details. 

TROUBLE  PROBABLE CAUSE  ISOLATION PROCEDURE  REMEDY 
Normal actuator motor continues to run after extension with NORMAL power applied Standby airstair motor continues to run after ladder rotation with NORMAL power applied Airstair ladders extend rapidly creating hazard to ground personnel with NORMAL power  Normal stair extend limit switch or normal airstair relay is defective Slow-down operating switch or slow-down operating relay defective Standby airstair relay defective Standby motor or standby retract relay defective  Slow-down operating switch or slow-down relay defective  Disconnect airstair connector D934 and check for continuity between pin 5 and pin 18 of plug P1. If not open, switch is defective. If open, relay is defective Check for 28 volts dc at terminal X1 of relay with control in extend position. If voltage is present, switch is defective. If voltage is not present, relay is defective Disconnect standby airstair motor connector J3 and measure 28 volts dc at pin 2 of J3. If voltage is present, relay is defective Partially retract airstair using standby power. If stair will not retract, see trouble under paragraph 4, Airstair Retraction Trouble Shooting Chart Check for 28 volts dc at terminal X1 of slow-down relay with control in normal extend position. If voltage is not present, switch is defective. If voltage is present, relay is defective  Replace or adjust switch. Refer to 52-61-151, Adjustment/Test. Replace relay Replace or adjust switch. Refer to 52-61-201, Adjustment/Test. Replace relay Replay relay Replace motor or relayReplace or adjust switch. Refer to 52-61-201, Adjustment/Test. Replace relay 
　
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