BENDIX SD-13-4796 Fiche De Données

CONTROL PORT

PROPORTIONING 

PISTON

INLET/EXHAUST VALVE

The letter identification and air hose connections are shown 

below for reference.
Bendix

Supply 

(to 

reservoir) 

   SUP

Delivery (to brake chamber) 

 

 

DEL

Service (to brake valve rear service delivery) 

SER

Control (to delivery of trailer supply valve)  

CON

The AR‑2

™

 valve is part of the R‑12

®

 family of relay valves 

which includes the R‑12

®

, R‑14

®

, BP‑R1

®

, and AR‑1

™

 

valves. The internal components of the relay portion of all 

of these valves are interchangeable with the R‑12

®

 valve 

and therefore the same basic components are used to 

service all of them.

The AR‑2

™

 valve incorporates various crack pressures to 

accommodate specific applications, the standard is 4 psi.

GENERAL
Because the AR‑2

™

 valve is actually a relay valve, the 

following description of operation refers to its function in 

the vehicle’s air brake system and does not address the 

separate antilock components and their operation. For a 

description of antilock operation, refer to the appropriate 

Service Data Sheet covering the electronic controller used 

with the AR‑2

™

 valve (SD‑13‑4785 covering the EC‑15

™

 

electronic controller). Other useful information regarding 

antilock system components used in conjunction with the 

AR‑2

™

 valve are contained in publications: SD‑13‑4793 

(Bendix

®

 M‑21

™

 antilock modulator); SD‑13‑4870 (Bendix

®

 

M‑32

™

 and M‑32QR

™

 antilock modulators); SD‑13‑4860 

(Bendix

®

 WS‑24

™

 wheel speed sensors); and SD‑13‑4754 

(Bendix

®

 WS‑20

™

 wheel speed sensors).

INITIAL CHARGING
During the initial build up of tractor system air pressure, 

reservoir air flows into the supply port and through internal 

body and cover passages to the blend back piston. When 

sufficient air pressure is applied to the blend back piston, 

it moves against the resistance of its spring until it comes 

to rest against the service piston.

Activating the trailer supply valve (dash control with red 

octagonal button), simultaneously charges the trailer 

and the AR‑2

™

 valve control port. Air entering the AR‑2

™

 

valve control causes the proportioning piston to move 

toward its stop in the cover. The integral inlet and exhaust 

valve is carried along with the piston until it seats and 

seals the exhaust passage. Continued movement of the 

proportioning piston opens the inlet seat. With the tractor 

and trailer air system fully charged the vehicle may be 

operated.

SPRING (NOT IN ALL 

MODELS)

RELAY PISTON

SERVICE PISTON

SERVICE PORT

SPRING

BLEND BACK 

PISTON

EXHAUST

INLET/EXHAUST VALVE

SUPPLY PORT

EXHAUST

DELIVERY PORT