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747-400 MAINTENANCE MANUAL
 WINDSHIELD WIPER ARM - INSPECTION/CHECK
_______________________________________
 1.  General_______
 A.  This task is an inspection/check for the windshield wiper arm. In this procedure, you will use a gage block to measure the pressure of the arm against the windshield.
 B.  It is possible that incorrect wiper arm pressure on the wiper blade will cause poor operation of the arm or will cause it to lift in flight. The windshield wiper arms apply approximately 10 pounds of pressure to the blade at the center of the travel and 5 pounds of pressure at the parked position. The wiper arm tension is not adjustable. Replace the arm if the force is not correct.
 TASK 30-42-02-206-001
 2.  Inspection/Check - Windshield Wiper Arm (Fig. 601)_______________________________________
 A.  Special Tools and Equipment
 (1) G30001-1, Block - Height Gage, Wiper Arm (plastic)
 B.  Standard Tools and Equipment
 (1)
Clean water spray (to make the windshield wet)

 (2)
Spring scale - 1 to 12 pounds or equivalent

 C.  Consumable Materials
 (1) G00507, Cloth - Lint Free (to prevent damage from the wiper arm)

CENTER WINDSHIELD POINT OF MEASUREMENT

1.39 |0.01 INCH
GAGE
ARM HEIGHT GAGE (PLASTIC BLOCK)
Windshield Wiper Arm Pressure Check
Figure 601

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747-400
MAINTENANCE MANUAL

 D. References
 (1)  
AMM 24-22-00/201, Manual Control

 (2)  
AMM 30-42-01/401, Windshield Wiper Blade

 (3)  
AMM 30-42-02/401, Windshield Wiper Arm

 (4)  
SSM 30-42-01

 (5)  
WDM 30-42-11

 E. Access
 (1)  Location Zone
 221 Control Cabin, LH - Outside of No. 1L Window
 222 Control Cabin, RH - Outside of No. 1R Window

 F. Procedure
 S 866-015
 WARNING:_______MAKE SURE TO OPEN THE CIRCUIT BREAKERS IN THIS STEP. YOU CAN GET AN ELECTRICAL SHOCK IF YOU TOUCH THE WINDSHIELD WHEN THE WINDOW HEAT POWER IS ON.
 (1)  Open these circuit breakers:
 (a)  
P6, Main Power Distribution Panel
 1) 6B34, WINDOW HEAT 1L PWR
 2) 6B17, WINDOW HEAT 1R PWR

 (b)  
P180, DC Power Distribution Panel
 1) 180H26, WDO HEAT CONT 1L
 2) 180H12, WDO HEAT CONT 1R

 S 866-003
 (2)  Supply electrical power (AMM 24-22-00/201).
 S 646-004
 CAUTION: MAKE SURE TO APPLY WATER TO THE WINDSHIELD BEFORE YOU OPERATE
_______ THE WIPERS. OPERATION OF THE WIPERS WITHOUT WATER CAN CAUSE DAMAGE TO THE WINDSHIELD.
 (3)  
Apply water to the windshield.

 (4)
Set the windshield wiper switch on the P5 overhead panel to LO.

 S 866-006

 (5)  
Open 7E1, WSHLD WIPER L or 7E25, WSHLD WIPER R circuit breaker on the P7, Overhead Circuit Breaker Panel to stop the wiper in approximately the center of windshield.

 S 866-005
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747-400 MAINTENANCE MANUAL
 S 026-007
 (6)  
Do this task: "Wiper Blade Removal" (AMM 30-42-01/401).

 S 226-016

 (7)  
Do a check of the wiper arm tension:

 (a)  
Put the arm height gage under the end of the wiper arm.

 (b)  
Adjust the gage until the wiper arm is on the 1.39-inch dimension (Fig. 601).

 (c)  
Attach a scale to the end of the wiper arm.

 (d)  
Slowly lift the wiper arm perpendicular to the windshield until it is clear of the gage.
　
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