Body Equipment Controls And Indicators

Maintenance of the M939 Series Vehicles
Page Navigation
22

primary brake system. Normal pressure is 90-130 psi.

(15) Defroster Control, opens vents to direct heated air at the

windshield.

(16) Heat Vent Control, controls the amount of heat blown into the

cab by adjusting the opening of heat ventilation doors.

(17) Fresh Air Vent Control, pulls out to open ventilation doors,

allowing outside air to circulate in the cab.

(18) Spring Brake Release Control is pushed in to release the

spring brakes independently of the mechanical parking brake.

The

control is used to release the spring brakes in order to test and

adjust the mechanical brake.

Body Equipment Controls and Indicators - Medium Wrecker.

NOTE

Key item numbers 1 through 12 and their function

coincide with figures 12 and 13 on pages 22 and

23.

(1) Trailer Power Outlet Receptacle (figure 12) provides electric

power for the trailer.

(2)

Towing Pintle Hook, is opened to attach the trailer towing

bar.

(3) Emergency Air Coupling, is connected by an air coupling hose

to the emergency coupling of a trailer or vehicle to be towed. This

connection permits the towing vehicle to charge the brake system of a

trailer or disabled vehicle with air.

(4) Trailer Air Valve Handles, are turned to release compressed

air to the trailer brake system.

On the M931 and M932, the valve

handle is placed in the down (open) position.