BENDIX BW1823 Manuale Utente

M-12

™

Modulator

EC-13

™

 

Controller

WS-20

™

 Speed Sensor

90 Degree

Confi guration

Connected to the EC-13

™

 controller via a wire harness, the 

modulator is essentially a high capacity, on/off air valve that 
incorporates a pair of electrical solenoids for control.  The 
solenoids provide the electric-air link between the antilock 
controller electronics and the air brake system. 

An optional indicator light can be connected to, and 
controlled by, the EC-13

™

 controller and serves as a 

means of advising the driver of the condition of the antilock 
system.

The data link function enables the EC-13

™

 controller to 

“report” its operating condition to a specialized, external 
computer in response to certain commands it receives.  
The EC-13

™

 controller data link confi guration conforms to 

S.A.E. standard J1708 and the protocol, or coded language 
used, conforms to S.A.E. standard J1587.  There are two 
connections to the EC-13

™

 controller devoted to the data 

link.  While the EC-13

™

 controller is capable of this function, 

and connections are provided, it is not always used.  Use 
of the data link is not essential for the EC-13

™

 controller 

to be functional. 

The Bendix

®

 EC-13

™

 controller provides axle braking 

control by using  four speed sensors and two modulators.  
By monitoring the rate of deceleration during braking, and 
subsequently adjusting the brake application pressure to 
each axle, the EC-13

™

 controller is able to provide improved 

braking while maintaining trailer stability.

The trailer’s rear axle brakes are controlled by the EC-13

™

 

controller and two modulators (M-12

™

 or M-12R

™

).  Like 

the standard service relay valve it replaces, the modulator 
delivers brake application pressure to the service chambers 
on each axle.  Two speed sensors on each axle “report” 
changes in acceleration and deceleration to the EC-13

™

 

controller.  If required, the EC-13

™

 controller adjusts the 

application pressure to either axle’s service brakes, via the 
modulators, based on the wheel behavior “reported” to it 
by the speed sensors on each axle.

The EC-13

™

 controller utilizes a “SELECT SMART” brake 

control philosophy for the trailer brakes.  This means 
that the EC-13

™

 controller will initially adjust application 

pressure to the service chambers on either an axle based 
on the speed information from the fi rst wheel to approach 
a locked condition.  The initial pressure adjustment will 
attempt to prevent either wheel on an axle from locking.  
If a substantial braking difference is detected between two 
wheels on an axle, the EC-13

™

 controller will override the 

fi rst air pressure adjustment and allow one wheel to lock.  
Both wheels including the locked wheel will continue to be 
monitored for speed and braking difference changes that 
would require pressure adjustments.  Each of the two axles 
is treated independent of the other.

During normal braking, the tractor brake valve simultaneously 
delivers air to the control port of the two trailer modulators.  
The modulators function the same as standard service relay 
valves and apply air to the service brakes.  The service 
brakes are thus applied.  

If the speed sensors do not detect an impending wheel 
lock up, the EC-13

™

 controller does not initiate any 

corrective action and the trailer comes to a stop in a normal 
fashion. 

If a service brake application is made and the speed 
sensors detect an impending wheel lockup on an axle, 
the EC-13

™

 controller will immediately begin modifi cation 

of the brake application using the antilock modulators at 
the affected axle(s).

WS-20

™

 Speed Sensor

Straight Confi guration