ELECTRICAL SYSTEM OPERATION

TM 9-2320-386-24-1-1

0005 00

ELECTRICAL SYSTEM OPERATION

The ESP series electrical system operates similarly to the M44A2 series vehicle electrical system.

Electrical component installation procedures and connections unique to ESP vehicles are found in this

manual.

SIMPLIFIED TEST EQUIPMENT/INTERNAL COMBUSTION ENGINES - REPROGRAMMABLE

(STE/ICE-R)

The STE/ICE-R system is a reprogrammable version of the STE/ICE system commonly used to test the

serviceability of standard M44A2, 2-1/2-ton vehicles. When in operation, test data are transmitted from

transducers to a permanently mounted Diagnostic Connector Assembly (DCA) located under the instrument

panel on the passenger side of the vehicle. The data are then transferred through a DCA cable to the Vehicle

Test Meter (VTM). The VTM uses the data received, and stored vehicle information, to give a result.

The STE/ICE-R can measure standard voltage, current, resistance, pressure, temperature, and speed.

Special tests, such as the compressor unbalance text and starter system evaluations, are also performed by

STE/ICE-R.

FRONT WINCH OPERATION

The ESP vehicle uses the same front winch commonly found on the M44A2 series vehicle. The front

winch is powered by a hydraulic system that transmits pressurized fluid from an engine-driven pump to

drive hydraulic winch motor attached to the rear of the winch at the input shaft. The pump is driven by the

engine and creates a vacuum that draws oil from the reservoir to a bypass valve. When the winch is not

engaged, the bypass valve routes the oil, via the filter, back to the reservoir. To engage the winch, the

lower air valve lever on the shift tower is pulled out and up, compressed air closes the bypass valve

reservoir return port and opens the control valve supply port. The control valve determines the direction of

drum rotation by routing the oil in either a clockwise or counterclockwise direction through the hydraulic

motor by engaging the upper air valve lever on the control tower. The upper air valve uses compressed air

to open and close the ports on the control valve.

POWER STEERING ASSIST SYSTEM OPERATION

The ESP series power steering assist operation is designed to ease manual steering operations when a

compressed air supply, 9 CFM minimum (0.252 cm) is available.

Major components of the system are the sealed torque valve, power assist steering cylinder, air safety

valve, and manual shutoff valve.

The torque valve senses the steering forces and automatically meters the appropriate amount of air to

the power assist steering cylinder. The power assist steering cylinder operates from the normal vehicle air

pressure, 120 psi (827 kPa).

The air safety valve conserves air if the air pressure in the reservoir falls below 65 psi (448 kPa). When

this occurs, steering automatically reverts to manual. When the air pressure builds to approximately 12 psi

(83 kPa) above cut-off setting, the valve will re-open and power steering assist is restored.

Closing the manual shutoff valve must be done prior to inspecting and servicing the components of the

power steering assist system. In the event of a failure to the system, the manual shutoff valve can be closed

and operation of the vehicle continued using manual steering.

SPLIT AIR-HYDRAULIC BRAKE SYSTEM OPERATION

The ESP vehicle uses the split air-hydraulic brake system. It provides two independent air and

hydraulic systems for actuation of the vehicle service brakes. One system actuates the front steering axle

brakes, while the second system actuates the forward-rear and rear-rear axle brakes.

With the split system, under normal conditions, the two systems work together, actuating all six service

brake positions concurrently as the brake pedal is depressed. The operator will notice no difference in

brake actuation, feel, or stopping distance compared to a single brake system.

Under unusual conditions, if one brake system fails and air or hydraulic pressure is lost, the second

brake system will still function. This will allow the vehicle to be brought to a controlled stop.

END OF WORK PACKAGE

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