COMPRESSED AIR AND BRAKE SYSTEM OPERATION (Contd)
FRONT EMERGENCY COUPLING - When vehicle is being towed, coupling receives compressed air from towing
vehicles brake system to charge its own brake system.
PRIMARY AIR RESERVOIR - Stores sufficient air pressure to allow operator to make normal brake applications,
should system pressure fail or engine stall.
PRIMARY FEED CUTOFF - Manually-operated valve used to isolate pressure leaks in primary air system from
draining wet tank (para. 3-12).
PRIMARY AIR RESERVOIR CHECKVALVE - Presents backflow of air from primary tank if wet system develops
SECONDARY FEED CUTOFF - Manually-operated valve used to isolate pressure leaks in secondary air system
from draining wet tank (para. 3-12).
SECONDARY AIR RESERVOIR CHECKVALVE - Prevents backflow of air from secondary tank if wet system
develops a leak.
REAR EMERGENCY COUPLING - When towing another vehicle, coupling allows pressurized air from wet tank to
charge towed vehicles wet tank.
SECONDARY AIR RESERVOIR - Stores enough air pressure in case constant pressure system fails or engine
stalls. The operator can make normal brake application before running out of air.
PRESSURE PROTECTION VALVE - Performs two functions:
Allows air pressure to build to 60-65 psi (414-448 kPa) before supplying air to auxiliary air-powered
Closes off auxiliary air system from other systems if an accessory fails and prevents loss of air from