TM 5-5420-280-23&P
0010 00
Hydraulic System Troubleshooting (Contd).
MALFUNCTION
TEST OR INSPECTION
CORRECTIVE ACTION
9. LOWER SUPPORT BOOM CYLINDERS WILL NOT EXTEND OR RETRACT (L14-A) OR (R2-H)
Step 1. Check hydraulic system for operating pressures.
Perform malfunctions 1 or 2.
Step 2. Check hydraulic hoses, tubing, and cylinders for damage or missing pins.
a. Replace hydraulic hoses or steel tubing if damaged. Refer to WP 0071 00.
b. Replace hydraulic cylinder(s) or pins if damaged or missing. Refer to WP 0096 00.
Step 3. Check that KY1, KY17, and KY20 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 launching procedures.
If all lights are lit on control valve solenoids, check potentiometer J2 position 2 to see if
damaged or out of adjustment. Adjust or replace potentiometer J2. Refer to WP 0093 00.
Step 4. Check for damaged control valve KY1, KY17, or KY20.
a. Manually operate control valve solenoids by locking KY1 control valve solenoid in on
position and depressing down KY17 and KY20 control valve solenoid buttons.
b. If control valve operates, refer to malfunction 9 in Electrical Troubleshooting
c. If control valve will not operate, replace control valve. Refer to WP 0075 00.
END OF TESTING
10. BOTTOM BRIDGE HALF WILL NOT MOVE ON LAUNCH BOOM (L16-H) OR (R7-H)
Step 1. Check for damaged launch beam pin wheel drive bracket or drive pins.
Repair or replace damaged pin wheel drive bracket or drive pins. Refer to WP 0028 00.
Step 2. Check for damaged rear pin wheel drive assembly.
Repair or replace damaged rear pin wheel drive assembly. Refer to WP 0082 00.
Step 3. Check that KY1, KY5, and KY7 hydraulic control valve solenoid LED lights are lit when
action button 2 or KY1 and KY6 hydraulic control valve solenoid LED light is lit when
action button 1 is depressed.
NOTE
Limit switch KA1 stops lower bridge half when deploying toward
rear of roller during launch and limit switch KA2 switches forward
pin wheel drive to rear pin wheel drive during launch and switches
rear pin wheel drive to forward pin wheel drive during retrieval.
If all lights are lit on control valve solenoids, check limit switch KA1 and KA2 to see if
damaged or out of adjustment. Adjust or replace limit switch KA1 and KA2. Refer to
Step 4. Check for damaged control valve KY1, KY5, KY6, or KY7.
a. Manually operate control valve by locking KY1 control valve in on position and
depressing KY5, KY6, or KY7 to operate pin wheel drives.
b. If control valves operate refer to malfunction 42 in Electrical Troubleshooting
c. If control valve will not operate, replace control valve. Refer to WP 0075 00.
