TM 10-3950-672-10
o. Electrical System. The electrical system is a 12-vdc operation with 12-vdc starting, consisting of an alternator
and one maintenance-free, 12-volt lead-acid battery. The system is single-wire, ground return-type, utilizing the
crane's structure as ground.
p. Heater/Defroster. The cab heater is located under the operator's seat. Hot water from the engine coolant
system flows through the coils of the heater.
Heated air is circulated in the cab by an electric motor-driven fan, controlled by heat level and fan speed control
knobs on the left side of the seat.
q. Antitwo-block System. The antitwo-block system provides a warning to the operator of an impending two-block
condition. The system consists of an antitwo-block switch, a relay, a buzzer, a warning indicator light, and the
associated wiring. The switch is held in the closed position by a weight suspended on a chain from the switch.
The closed switch maintains the relay energized, which silences the buzzer and prevents illumination of the
indicator light. As the hook block comes closer to the boom tip, it contacts the weight and the switch springs
open. This action deenergizes the relay, which sounds the warning buzzer, and illuminates the WARNING
indicator light on the PAT panel mounted on the main control panel.
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