TM 5-5420-280-23&P
0008 00
Electrical System Troubleshooting (Contd).
MALFUNCTION
TEST OR INSPECTION
CORRECTIVE ACTION
30. RCU WILL NOT LOWER LAUNCH BOOM TO RETRIEVAL POSITION (R4-A+H+M)
Step 1. Check that KY1 and KY18 hydraulic control valve solenoid LED lights are lit when action
button 2 is depressed.
NOTE
Potentiometer JR2 is used to stop launch boom at a set position in
the retrieval procedure.
a. If both lights are lit on control valve solenoids, check potentiometer JR2 position 6 to see
if damaged or out of adjustment. Adjust or replace potentiometer JR2. Refer to
b. If potentiometer JR2 is operating and control valve solenoid lights are lit, refer to
malfunction 7 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 control valve solenoid LED lights are out when action button 2
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
(WP 0122 00) and repair or replace wires (WP 0053 00) or adjust potentiometer
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 wire between KL-1 buss bar pins 18, 34, 35, and 48 IQAN-XP connector pins 22,
15, 17, and 1. Replace wire if damaged. Refer to WP 0053 00.
END OF TESTING
31. RCU WILL NOT RAISE NEAR-SHORE END OF BRIDGE WITH WINCH WIRE ROPE (R5-H)
Step 1. Check if winch electrical harness, control cable, or power supply cable are loose or damaged.
If loose or damaged, connect or replace winch electrical harness, control cable, or power
supply cable. Refer to WP 0065 00, Electrical System Schematic WP 0122 00, and Winch
Electronic Box Schematic WP 0124 00.
Step 2. Check if power supply cable is suppling power to winch electronic box.
a. If power supply cable has no power, check if fuse is blown. Replace 8 Amp fuse.
b. If fuse is good, repair or replace power supply cable. Refer to WP 0065 00, Electrical
System Schematic WP 0122 00, and Winch Electronic Box Schematic WP 0124 00.
Step 3. Check if rope loop sensor light is lit when action button 1 is depressed.
a. If light is not lit, check for loose connector on rope-loop sensor.
b. If light is lit, check if rope loop sensor is out of adjustment or damaged and adjust or
replace rope loop sensor. Refer to WP 0064 00.
Step 4. Check if winch system has hydraulic pressure to winch control block, refer to
malfunction 5 in Hydraulic System Troubleshooting (WP 0010 00).
Change 1