TRANSPORTING LOADS (Continued).
Stopping. In normal operation, when the driver applies the brakes, the prime mover and the
trailer brakes are applied at the same time. Brake pressure should be applied gradually and
smoothly. The trailer brakes may be applied separately by using the trailer hand brake control
lever in the prime mover. Extreme caution should be exercised when using only the trailer
brakes. Some benefit may be gained on slippery surfaces by slowly applying the trailer brakes
before the prime mover brakes, reducing the possibility of jackknifing the trailer. However, it is
very dangerous to use only the trailer brakes on long downgrade. Doing so will cause the trailer
brakes to heat up and fade. The prime mover brakes alone will not be able to stop the
combined vehicle load. Selecting a lower gear before beginning a long downgrade is the safest,
most effective way to maintain control of the vehicle combination.
Parking. When the prime mover and the trailer are to be parked and left unattended, set the
parking brake on the prime mover and the trailer.
Visibility from the prime mover is significantly reduced when backing, whether the
trailer is loaded or not. Proper procedures must be followed and extreme caution
used when backing to prevent damage to equipment and injury to personnel.
Backing. When backing, use the assistant driver as a ground guide. Adjust rear view mirrors
before backing. Use slow speed and extreme caution when backing this combination.
Antilock Braking System (ABS). The ABS is an electronic system that monitors and controls
wheel speed during braking and wheel lock situations. The system improves vehicle stability and
control by reducing wheel lock during braking. The ABS includes an electronic control unit
(ECU) that is combined with a dual modulator valve assembly. Four wheel speed sensors
provide input to the ECU. When the ECU detects a wheel lockup during a hard braking situation,
the ECU activates the appropriate modulator valve to controll air pressure to the braking system.
The ECU is to be replaced and is not serviced.
In the event of a malfunction in the ABS , the ABS in the affected wheel is disabled and that
wheel still has normal brakes. The other wheels keep the ABS function.
An ABS indicator lamp located on the left rear corner of the trailer, lets the driver know through
a series of blink codes the status of the system on initial startup. A warning label is affixed to the
trailer near the ABS indicator lamp to identify the meaning of the blink codes.