TM 5-5420-280-23&P
0008 00
Electrical System Troubleshooting (Contd).
MALFUNCTION
TEST OR INSPECTION
CORRECTIVE ACTION
18. RCU WILL NOT LOCK LAUNCH BOOM INTO COUPLING POSITION (L14-A) AND (L15-A)
Step 1. Check that KY1, KY17, and KY23 hydraulic control valve solenoid LED lights are lit when
action button 1 is depressed.
NOTE
Potentiometer JR2 is used to stop launch boom at a set position in
the launching procedures.
a. If all lights are lit on control valve solenoids, check potentiometer JR2 position 3 to see if
damaged or out of adjustment. Adjust or replace potentiometer JR2. Refer to WP 0093 00.
b. If potentiometer JR2 is operating and control valve solenoid lights are lit, refer to
malfunction 7, Hydraulic System Troubleshooting (WP 0010 00).
c. Check operation of IQAN-XP and IQAN-XS LED lights. Refer to WP 0004 00 step h.
Step 2. Check to see if only one or no lights are lit when action button 1 is depressed.
a. If light is out, check for 24 volts at control valve solenoid.
b. If connector has 24 volts, replace control valve solenoid or hydraulic control valve. Refer
to WP 0075 00.
c. If connector has no voltage, check wires at KL-1 buss bar pin 1 for KY1 control valve
solenoid, KL-1 buss bar pin 17 for KY17 control valve solenoid, KL-1 buss bar pin 23 for
KY23 control valve solenoid, and KL-1 buss bar pins 34, 35, and 48 for JR2
potentiometer. Refer to Electrical System Schematic (WP 0122 00) and repair or replace
wires (WP 0053 00) or adjust potentiometer (WP 0093 00).
d. Check wire between KL-1 buss bar pin 1 and IQAN-XS connector pin 20. Replace wire if
damaged. Refer to WP 0053 00.
e. Check wires between KL-1 buss bar pins 17, 23, 34, 35, and 48 and IQAN-XP connector
pins 34, 27, 15, 17, and 1. Replace wires if damaged. Refer to WP 0053 00.
END OF TESTING
