TEST OR INSPECTION
MAIN WINCH CIRCUIT (MAIN HYDRAULIC SYSTEM Continued
Test combination control valve. Install pressure gage in test gage port no. 50 at main winch level winder. Remove hose no.
21A from valve, and plug outlet of valve. If no pressure is indicated on
gage when operating hydraulic system. it indicates a
faulty combination control valve. For location of test gage port. refer to view L. fig. 3-8.
Replace and adjust combination control valve. Refer to paragraph 3-6. 3-10. and 3-10.1.
Notify next higher level maintenance activity or major unit commander.
Test control valve. Install pressure gage in combination control valve port no. 7. If no pressure is established on gage when
actuating control valve. but if pressure is established when removing hose no. 21A from control valve and plugging outlet, it
indicates a faulty main winch control valve Replace main winch control valve. See view F, figure 3-20, and refer to TM 9-2350-
256-34-1, Medium Recovery Vehicle, M88A1.
Test for hydraulic motor failure. Remove hose no. 47 from rear of hydraulic motor. A large volume of oil discharged from port
when main winch control valve is engaged indicates a faulty motor.
Replace hydraulic motor. Refer to TM 9-2350-256-34-1. Medium Recovery Vehicle, M88A1.
Inspect system selector valve lever for improper position.
Place system selector valve lever in MAIN position.
Mechanical failure of main winch gear train.
Remove main winch and spade assembly. Refer to TM 9-2350-256-34-1, Medium Recovery Vehicle, M88A1.
b. Replace main winch. Refer to paragraph 3-6.
MAIN WINCH PAYS IN AND OUT UNDER NO LOAD, BUT WILL NOT PAY IN OR OUT UNDER LOAD
Prepare the hydraulic system for operation per TM 9-2350-256-10. Pay special attention to item 3. page 2-79.
a. Verify that the APU emergency winch control valve is in NORMAL OPERATION position. Refer to fig. 2-26 of TM 9-2350-
Main winch will be in low gear.
Conduct all hydraulic operations in 1800 RPM or governed engine speed.
TM 9-2350-256-10 states minimum engine speed for winching operations is 1500 RPM.
Conduct all hydraulic operation verifications with a hydraulic reservoir temperature of 1 10 F to 1200F.
Verify main hydraulic pressure in accordance with step 8 of malfunction no. 1.
If hoist winch, boom, and spade operate properly, proceed to steps 9 through 14 of malfunctionno. 1.
This would indicate satisfactory main hydraulic pump operation.
If the problem is still unresolved and system pressure has been verified to be 1950 to 2050 psi perform the following:
a. Install pressure gage (NSN 4910-00-766-3355) in test port no. 50 at main winch level winder. (For location of test gage port.
refer to view L fig. 3-8).
Adjust main winch. Refer to paragraph 3.10.1, b. step 3.
Verify pressure reading of approximately 1425 psi. The pressure shall be stable. Refer to paragraph 3.10.1, c,step 3.
Extremely low pressure (below 1300 psi) would be an indication of improper relief valve setting or a faulty combination
Fluctuating and unstable hydraulic pressure is an indication of a faulty combination control valve.
d. If fluctuating and unstable hydraulic pressure is experienced, replace the main winch combination control valve.
e. If extremely low pressure is experienced (below 1300 psi). readjust the main winch pressure to 1400 psi. The pressure
must be stable and without fluctuation. If readjustment cannot be accomplished. replace the main winch combination control
valve. Adjustment to the valve is accomplished by cutting the lockwire to the acorn nut. removing the nut and loosening the
locknut. Turn the adjusting screw 1/8 of a turn at a time for adjustment. Turn the screw "in" to increase pressure. (Turning
"out" decreases pressure). the final pressure setting should be verified with the locking nuttightened. Secure the acorn nut
Do not exceed a 1400/1450 psi pressure relief setting. Excessive pressure will produce main winch cable
pull valves in excess of vehicle specification-bodily injury could occur.
Readjust the brakes for proper function Refer to TM 9-2350-256-20.
The hydraulic pressures stated above are for troubleshooting only and shall not be used as a substitute for
load checks to see main winch cable line pull valve.
Change 5 2-6.2