SECTION III: PRINCIPLES OF OPERATION
Generator voltage regulators. The M88A1 has either a single or dual voltage system. In the dual system -there are
two solid-state generator voltage regulators which maintain generator output voltage at a constant 28 + 0.7 V dc.
One controls the generator voltage output of the engine and the other the generator voltage output of the APU. In
the single system, a single voltage regulator controls both the engine and APU generator voltage output. The
voltage regulators are mounted at the left rear of the engine compartment.
Starter assembly. The 24-V, waterproof starter assembly is mounted on the lower left side of the engine toward the
rear. It is a heavy-duty, solenoid-operated, enclosed, shift-lever-type engine starter. The motor utilizes 12 brushes
retained in 6 brush holders which are accessible through inspection plugs in the motor frame. The drive clutch is a
heavy-duty, over-running type with adjustable pinion clearance.
Neutral safety switch. The neutral safety switch, mounted on the brake assembly, functions as a safety switch to
prevent starting the engine while the transmission shift control is in any shift position other than P (park).
Master relay. The master relay is located in the left rear of the engine compartment. It controls primary power to all
electrical systems and components with the exceptions of the personnel heater system, the MASTER switch, and
the slave receptacle.
Batteries. Six 12-V batteries are connected in a series-parallel circuit to give the vehicle a 300-A-hr source of 24-V
dc power. The batteries are located in the left side of the engine compartment.
GAGE AND SWITCH PANELS
Gage panel (located to the left of the steering control at the driver's position). The gage panel mounts the following:
Fuel level gage
Engine and transmission temperature and pressure gages
Battery generator indicator
Speedometer and tachometer
Mechanical transmission oil pressure warning light
Master warning light
Three instrument panel lights
Fuel selector switch
Switch panel (located to the right of the driver's steering control). The switch panel mounts the following:
Main light switch
Auxiliary light switch
Fuel cutoff switch
Fuel pump switch
Five circuit breakers
Master relay indicator light
Blackout (B.O.) selector switch
SENDING UNITS AND WARNING INDICATORS
Sending units. Sending units for the gage panel are mounted on the engine, transmission, and forward and right
rear fuel tanks to indicate the engine and transmission oil temperatures, pressures, and fuel levels.