Abs/Atc System (Anti-Lock Brakes) - Holiday Navigator 2003 Owner's Manual

The motorhome is equipped with an anti-lock braking system (ABS) and
automatic traction control system (ATC). The ABS system monitors wheel
rotation speeds by using a 100-tooth magnetic tone ring mounted to the hub.
Revolving with the wheel, the magnetic tone ring is polarized giving positive
and negative pulsations. A stationary sensor is mounted adjacent to the tone
ring monitoring the magnetic pulses. The pulses are monitored by the ABS
electronic control unit (ECU).
The ECU monitors all available wheel sensors at the rate of 100 times per
second. The ECU controls Pressure Modulator Valves. Pressure Modulator
Valves have two electric over air solenoids, a hold solenoid and a release solenoid.
The modulator valves are open under normal braking, allowing a straight
through air signal from the treadle valve to the brake chamber. Should a wheel
lose traction under a braking application, the ECU will energize the hold solenoid
of the Pressure Modulator Valve to interrupt the air signal from the treadle
valve to the brake chamber. The release solenoid vents the existing air signal,
at the brake chamber to the atmosphere, allowing the skidding tire to regain
traction. Skidding tires have less tractive efficiency. It is possible, under certain
conditions, to have the wheel(s) skid with a normal functioning ABS system.
The ABS itself does not apply additional braking power. The purpose of the
ABS is limiting brake torque to prevent wheel locking that results in the loss
of lateral stability, and increased stopping distances. Cautious driving practices
and maintaining adequate safe distances when following vehicles is the key to
safe vehicle operation.
WARNING: The ABS/ATC system is designed to increase tire
to road surface traction. The system cannot overcome naturally
occurring laws of physics. The ABS/ATC system combined
with safe driving practices reduce the possibility of wheel skid
and loss of lateral stability.
ABS Component Function:
• Speed sensors and tone rings on each wheel monitor wheel rotation.
• Each speed sensor communicates wheel rotation pulses to the
Electronic Control Unit.
• ECU receives the speed sensor inputs, interprets the signal pulses,
calculates speed and acceleration rates of each wheel.
• Based on the speed sensor input, the ECU detects impending
wheel lock and operates the ABS Modulator Valves required for
proper control. The Modulator Valves can be operated in the air,
release or hold modes to regulate air pressure to the brake chambers.
• The braking force is applied at a level which minimizes the
stopping distances while maintaining as much lateral stability as
possible.
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N A V I G A T O R 2 0 0 3
Chassis Information
ABS/ATC SYSTEM
(Anti-lock Brakes)
090307
1 0 • 3 9 9