Anti-Lock Brake System (Abs) - Landoll 334C Operator's Manual

3-22 ANTI-LOCK BRAKE SYSTEM (ABS)

Vehicle standards FMVSS No. 121, anti-lock
brake system requires all trailers with air brake
systems to have ABS after March 1, 1998. Each
trailer (including a trailer converter dolly) shall be
equipped with an anti-lock brake system that con-
trols the wheels of at least one axle of the trailer.
Wheels on other axles of the trailer may be indi-
rectly controlled by the anti-lock brake system.
NHTSA Docket 92-29; notice 11 published
September 23, 1996 specifies the ABS warning
light be mounted near the rear of the left side of
the trailer (See Figure -).
•
Decal or lens marking with ABS to iden-
tify the lamp.
•
The lamp must illuminate one time when-
ever power is supplied to the ABS. When
the light remains on while power is sup-
plied and the vehicle has been pulled
faster than 4 mph, there is a malfunction
to the system.
The ABS used on the semitrailer is a commer-
cial unit. Single axle trailers use a two wheel sen-
sor and one valve system. The valve is an ABS re-
lay valve with integrated electronic control unit. The
wheel sensors check for wheel lock-up. The valve
modulates both sides of the trailer if either side
starts to lock-up.
Tandem axle and triple axle trailers use a four
wheel sensor and two valve system. Sensors are
located on the front and rear axles. Even triple axle
trailers with lift axles have wheel sensors on the
front and rear axles because the ECU can detect
when the axle is lifted and will disregard it's read-
ing. One of the valves is an ABS relay valve with
integrated electronic control unit. The other valve is
an ABS relay valve that is controlled by the elec-
tronic control unit on the first valve. The valve with
the integrated electronic control unit controls the
brakes on the right side of the trailer, the other
valve controls the brakes on the left side of the
trailer. For example, if either the front or rear axle
on the right side of the trailer begin to lock-up, the
valve with the integrated electronic control unit will
modulate all the brakes on the right side of trailer
to prevent the lock-up.
It is important that all the wheel sensor wires
go to the correct connection on the integrated elec-
tronic control unit so the valves modulates the cor-
rect brakes and so the diagnostic codes are cor-
rect.
The ABS is constant powered by the auxiliary
(blue) circuit, center pin on the semitrailer seven
way electrical connector. This circuit must be hot
whenever the tractor key switch is on. This circuit
must also not be used to power any additional
electrical devices while the semitrailer is moving
forward. However, additional devices such as re-
mote controls may be powered from the auxiliary
circuit while the semitrailer is stationary. Back up
power to the ABS is supplied through the stop
lamp (red) circuit, No. 4 pin on the seven way con-
nector, and ground is supplied by the white wire,
No. 1 pin.
CAUTION
THE AUXILIARY (BLUE) CIRCUIT IS
FOR POWERING THE SEMITRAILER
ABS. THIS CIRCUIT MUST BE HOT
WHEN THE TRACTOR KEY SWITCH IS
ON. NO OTHER ELECTRICAL DEVICES
MAY BE POWERED BY THIS CIRCUIT
WHILE THE SEMITRAILER IS MOVING
FORWARD.
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