RECOVERY VEHICLE, FULL TRACKED: MEDIUM, M88A1
ELECTRICAL SYSTEMS AND CIRCUITS THEORY OF OPERATION
Electrical Systems and Circuits
Charging/Starting System and Vehicle Batteries
Engine generator. The generator is an air-cooled, 28-V, dc-rated, 300-A, field-regulated unit. It is mounted on the right
side of the engine near the flywheel end, and is gear driven by the engine. An integral blower, an air intake duct, and
an outer boot and duct provide a means of cooling the generator. The electrically operated blower draws air from the
crew compartment, forces it through the generator, and exhausts it upward through an outlet near the right camshaft
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
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.