(d)  
Put the thermal switch in the bond.

 S 434-019
 (5)  
Connect the wires to the thermal switch.

 S 864-021

 (6)  
Close these circuit breakers and remove DO-NOT-CLOSE tags:

 (a)  
WINDOW ANTI-ICE R4 R5

 (b)  
WINDOW ANTI-ICE L4 L5

 S 724-024
 (7)  Do a test of the thermal switch.
 (a)  
Push the applicable window heat switch to the ON position.

 (b)  
Monitor the inner temperature of the window, adjacent to the thermal switch.

 NOTE: The thermal switch opens when the temperature of
____ the window is between 100 and 120 degrees F. This will occur more than 15 minutes after you turn the window heat on.
 (c)  Make sure the temperature stays between 80 and 120 degrees F.
 1)  Replace the thermal switch if the temperature is more than 125 +/- 1 degrees F.
 NOTE: Cool external temperatures can make the
____ thermal switch keep the window too hot. Do not replace a thermal switch when the temperature of the window is between 120 and 124 degrees F.
 (d) Push the applicable window heat switch to the OFF position.
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 30-41-31
 ALL  ú ú 01 Page 405 ú Nov 15/90
BOEING PROPRIETARY - Copyright (C) - Unpublished Work - See title page for details.
A
737-300/400/500MAINTENANCE MANUAL
 WINDSHIELD WIPER SYSTEM - DESCRIPTION AND OPERATION
___________________________________________________
 1.  General_______
 A.  Windshield wipers are provided to maintain a clear area on the pilots' No. 1 windows during takeoff, approach and landing in rain or snow. Each wiper is operated by a separate system to ensure that clear vision through one of the windows will be maintained in the event of a system failure. The wiper blades clear a patch approximately 13-1/2 inches wide through an arc of 84 |4 degrees.
 B.  Both wiper systems are operated by a switch located on the overhead panel. The switch provides selection of the wiper action speeds. The switch also controls the PARK position when the system is not in use.
 C.  Each windshield wiper system consists of these components:
 (1)
Drive motor and torque converter assembly

 (2)
A control switch assembly

 (3)
Windshield wiper assembly

 (4)
Resistor box

 D.  Speed control is accomplished by changing the voltage applied to the windshield wiper motor by means of resistors. The required resistance is connected into the motor circuit by turning the windshield wiper switch to a selected position. The rotary motion of the drive motor is transmitted to the converter which reduces the shaft speed and changes rotary motion to an oscillating motion of the whindshield wiper arm.
 E.  A second method for maintaining clear windows in heavy rain is by the use of rain repellant (Ref 30-43-00, Rain Repellant System).
 2.  Motor-Converter Assembly________________________
 A.  The wiper assembly for each system is driven by a motor-converter assembly. The motor-converter assembly consists of a 28-volt dc variable speed electric motor and torque converter coupled together by a connector sleeve and assembled on a support fitting. Each assembly is mounted on a bracket on the respective window sill close to the inner surface of the skin.
 B.  Each motor is equipped with two radio noise filters, an automatically resetting thermal overload switch, and a cam actuated switch. The thermal switch temporarily opens the motor field circuit when the motor temperature exceeds 300°F, or when the field current exceeds 8 to 10 amps. The cam actuated switch is a two-pole two-position microswitch. The operating cam is driven by reduction gearing in the motor to coincide with the wiper cycle. One pole of the switch is closed when the motor is in any part of the wiper cycle other than PARK. The other pole of the switch is closed only when the motor is in the PARK position of the cycle. The switch is used in conjunction with the system control switch to stop the motor with the wipers in the PARK position when the system is not in use.
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