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3-16 REAR IMPACT GUARD SYSTEM
Vehicle standards FMVSS No. 224, Rear Im-
pact Protection, requires all trailers manufactured
after January 26, 1998 shall be equipped with a
rear impact guard certified by the manufacturer as
meeting FMVSS No. 223, Rear Impact Guards.
The guard, or bumper, (See Figure 3-7) meets the
following requirements:
·
a minimum of 4 inches vertical height
·
extend laterally to within 4 inches of the
sides of the trailer
·
a ground clearance of no more than 22
inches
·
placed no more than 12 inches from the rear
of the trailer
·
capable to deflect 5 inches
3-17 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 3-7).
·
decal or lens marking with ABS to identify
the lamp
·
the lamp must illuminate one time whenever
power is supplied to the ABS. At any time
the light remains on when power is supplied
there is a malfunction to the system.
The standard also specifies minimum force and
energy absorption requirements for the guard. A
DOT decal certifies that the guard meets FMVSS
No. 223 and 224 standards. The decal is placed
and must remain at all times on the forward fac-
ing surface of the guard, 12 inches inboard of the
curb side and of the guard. See Figure 3-7 for lo-
cation of decals.
Replace any component that does not allow
the above minimum requirements to be met. Any
hardware that holds the rear impact guard and be-
comes damaged or becomes loose shall be re-
moved and replaced. The 3/4" grade 8 screws that
hold the bumper energy pack shall be loctited and
torqued to 280 ft.-lbs.
DANGER
ALWAYS CHECK THE CONDITION OF
THE REAR IMPACT GUARD SYSTEM.
IF GUARD SYSTEM HAS BEEN DAM-
AGED, IT MUST BE REPLACED. FAIL-
URE TO MAINTAIN GUARD SYSTEM
MAY RESULT IN INJURY OR DEATH
TO OTHERS.
Tandem axle trailers use a four sensor, two
modulator system. Sensors are located at each
hub of the front and rear axles, and each modula-
tor controls one side of the trailer.
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 keyswitch 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.
3-15
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