TM 5-5420-280-23&P
0008 00
Electrical System Troubleshooting (Contd).
MALFUNCTION
TEST OR INSPECTION
CORRECTIVE ACTION
8. RCU WILL NOT LOWER LAUNCH BOOM TO LAUNCH POSITION (L6-A) (Contd)
Step 2. Check to see if one or more control valve solenoid LED lights are out 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 18 for KY18 control valve solenoid, and KL-1 buss bar
pins 34, 35, and 48 for potentiometer JR2. Refer to Electrical System Schematic
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 18, 34, 35, and 48 and IQAN-XP connector pins
22, 15, 17, and 1. Replace wires if damaged. Refer to WP 0053 00.
END OF TESTING
9. RCU WILL NOT MOVE LOWER BRIDGE HALF (L8-A)
Step 1. Check that KY1, KY4, and KY23 hydraulic control valve solenoid LED lights are lit when
action button 1 is depressed.
NOTE
Limit switch KA2 switches front pin wheel drive to rear pin wheel
drive as lower bridge half moves to rear.
a. If all lights are lit on control valve solenoids, check limit switch KA2 to see if damaged or
out of adjustment. Adjust or replace limit switch KA2. Refer to WP 0056 00.
b. If limit switch KA2 is operating and control valve solenoid LED light is lit, refer to
malfunction 6 in 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 one or more of the control valve solenoid LED lights are out 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 4 for KY4 control valve solenoid, KL-1 buss bar pin 23 for
KY23 control valve solenoid, and KL-1 buss bar pin 26 for limit switch KA2. Refer to
Electrical System Schematic (WP 0122 00) and repair or replace wires (WP 0053 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 26, 23, and 27 and IQAN-XP connector pins 3,
26, and 24. Replace wires if damaged. Refer to WP 0053 00.
END OF TESTING
