BENDIX SD-13-4795 Manuel D’Utilisation

provides for rapid exhaust of control air pressure from 
above the relay piston. The standard AR-1

™

 valve is offered 

with a 4 psi crack pressure, however, with the addition 
of various springs beneath the relay piston, higher crack 
pressures are possible.

The AR-1

™

 valve’s internal components are interchangeable 

with the R-12

®

 and R-14

®

 relay valves, therefore, the same 

maintenance kit is used to service all three valves.

Brake application air enters the AR-1

™

 valve’s service port 

and encounters the exhaust diaphragm which fl exes  in 
response to the incoming air, sealing the exhaust passage 
in the cover. Air fl ows around the exhaust diaphragm and 
moves through a passage in the cover to the top of the 
relay piston. In response to air pressure, the relay piston 

moves into contact with the exhaust portion of the inlet and 
exhaust valve. With the exhaust passage sealed, continued 
movement of the relay piston unseats the inlet portion of 
the inlet and exhaust valve, allowing supply air from the 
reservoir to fl ow  out  the AR-1

™

 valve’s delivery ports to 

the antilock modulators and then to the brake actuators. 
(See Figure 3)

The air pressure being delivered to the antilock modulators 
and brake actuators is also present beneath the relay 
piston. When the air pressure above and below the relay 
piston is equal, the piston moves slightly allowing the inlet 
valve to return to its seat. The exhaust valve remains 
closed. With both the inlet and exhaust valves closed, air 
pressure in the antilock modulators and brake actuators 
is held stable and neither increases nor decreases. (See 
Figure 4)

EC-15

™

 ANTILOCK 

CONTROLLER

TYPICAL 

MOUNTING 

BRACKET

AR-1

™

 ANTILOCK RELAY 

VALVE