TM 5-5420-280-23&P
0008 00
Electrical System Troubleshooting (Contd).
MALFUNCTION
TEST OR INSPECTION
CORRECTIVE ACTION
15. RCU WILL NOT LOWER SECONDARY BOOM (L13-H)
Step 1. Check that KY1 and KY15 hydraulic control valve solenoid LED lights are lit when action
button 1 is depressed.
NOTE
Limit switch KA6 stops secondary boom and once lowered, actuates
launch boom to go up.
a. If both lights are lit on control valve solenoids, check limit switch KA6 to see if damaged
or out of adjustment. Adjust or replace limit switch KA6. Refer to WP 0056 00.
b. If limit switch KA6 is operating and control valve solenoid lights are lit, refer to
malfunction 11 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 only one of the lights is 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 15 for KY15 for control valve solenoid, and KL-1 buss bar
pin 30 for KA6 limit switch. Refer to Electrical System Schematic (WP 0122 00) and
repair or replace wires (WP 0053 00).
d. Check wires between KL-1 buss bar pins 1 and 30 and IQAN-XS connector pins 20
and 22. Replace wires if damaged. Refer to WP 0053 00.
e. Check wire between KL-1 buss bar pin 15 and IQAN-XP connector pin 33. Replace wire if
damaged. Refer to WP 0053 00.
END OF TESTING
16. RCU WILL NOT LIFT LAUNCH BOOM TO COUPLING POSITION (L14-A)
Step 1. Check that KY1 and KY17 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 7 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 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.
Change 1