TM 5-5420-280-23&P
0008 00
Electrical System Troubleshooting (Contd).
MALFUNCTION
TEST OR INSPECTION
CORRECTIVE ACTION
13. RCU WILL NOT LOWER LAUNCH BOOM TO PRE-COUPLING POSITION (L12-A)
Step 1. Check that KY1 and KY16 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 4 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 13 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.
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 16 for KY16 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).
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 pin 15 and IQAN-XP connector pin 33. Replace wire if
damaged. Refer to WP 0053 00.
END OF TESTING
14. RCU WILL NOT DEPLOY LIFTING CYLINDERS (L14-A)
Step 1. Check that KY1, KY17, and KY20 hydraulic control valve solenoid LED lights are lit when
action button 1 is depressed.
a. If all lights are lit on control valve solenoids, refer to malfunction 9 in Hydraulic System
Troubleshooting (WP 0010 00).
b. 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.
a. If only one or two lights are lit, check for 24 volts at control valve solenoids with light off.
b. If connector has 24 volts, replace control valve solenoid or hydraulic control valve. Refer
to WP 0075 00.
c. Check operation of IQAN-XP and IQAN-XS LED lights. Refer to WP 0004 00 step h.
d. 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, and KL-1 buss bar pin 20
for KY20 control valve solenoid. Refer to Electrical System Schematic (WP 0122 00) and
repair or replace wires (WP 0053 00).
e. Check wire between KL-1 buss bar pin 1 and IQAN-XS connector pin 20. Replace wire if
damaged. Refer to WP 0053 00.
f. Check wires between KL-1 buss bar pins 17 and 20 and IQAN-XP connector pins 34 and
40. Replace wires if damaged. Refer to WP 0053 00.
END OF TESTING
Change 1
