Table 4-2 Unit Troubleshooting - Continued
TEST OR INSPECTION
HYDRAULIC SYSTEM - Continued
LADDER LOWERS AND RETRACTS SLOWLY
Extremely cold hydraulic oil will affect operation of the ladder.
Operate unit to bring oil to operating temperature.
Check for restriction in hydraulic tank return hose or filter.
Replace hydraulic filter (see para 4-189).
Replace return hose (see para 4-9).
LADDER WILL NOT LOWER OR RETRACT
Step 1. Check position of manual override.
Ensure manual override handle is in neutral position and moves freely.
Step 2. Check that aerial system is engaged.
Ensure DIVERTER VALVE AERIAL/OUTRIGGER switch is in AERIAL position.
Step 3. Check for possible aerial interlock malfunction.
Refer to electrical troubleshooting procedures to test system.
Step 4. Check hydraulic oil level in tank.
Refill to proper level (Chapter 3, Lubrication Instructions).
LADDER WILL NOT LOWER
Step 1. Check that locking solenoids are released.
Refer to electrical troubleshooting procedures to test solenoid valves.
Step 2. Check operation of LOWER/RAISE ladder control valve.
Refer to Direct Support maintenance for repair or replacement.
Step 3. Check if excessive fluid flow has forced a hydraulic fuse in one or both hoist cylinders to
With the system pressurized, raise the ladder slightly then lower it.