TM 5-5420-280-23&P
0008 00
Electrical System Troubleshooting (Contd).
MALFUNCTION
TEST OR INSPECTION
CORRECTIVE ACTION
7. RCU WILL NOT DEPLOY BRIDGE HALF (L5-A)
Step 1. Check that KY1 and KY4 hydraulic control valve solenoid LED lights are lit when action
button 1 is depressed.
NOTE
Limit switch KA1 stops lower bridge half when driving out during
first launch step.
a. If both lights are lit on control valve solenoids, check limit switch KA1 to see if damaged
or out of adjustment. Adjust or replace limit switch KA1. Refer to WP 0056 00.
b. If limit switch KA1 is operating and control valve solenoid lights are lit, refer to
malfunction 10 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 1
is depressed.
a. If lights are 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, and KL-1 buss bar pin 25
for KA1 limit switch. 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 buss bar pins 3 and 25 and IQAN-XP connector pins 37 and 2.
Replace wires if damaged. Refer to WP 0053 00.
END OF TESTING
8. RCU WILL NOT LOWER LAUNCH BOOM TO LAUNCH POSITION (L6-A)
Step 1. Check that KY1 and KY18 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 both lights are lit on control valve solenoids, check potentiometer JR2 position 2 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.
