Modulator Valve

Based upon wheel speed input signals, RWAL control unit regulates hydraulic brake pressure to both rear wheels. Under normal conditions, RWAL system functions like a conventional brake system.

Normal wheel speed-to-acceleration/deceleration braking is programmed into RWAL control unit memory. If the difference between optimum braking rear wheel speed and actual braking rear wheel speed exceeds programmed limits, RWAL system will enter anti-lock mode.

During anti-lock mode, pressure in the rear wheel hydraulic circuit is regulated by the control unit through the modulator valve. This prevents rear wheel lock, while providing maximum stopping and directional stability. Modulator valve is located in brake lines between master cylinder and load sensing proportioning valve at rear of vehicle. Modulator actually consists of 2 valves: a release valve which dumps pressure and a hold valve which maintains rear wheel hydraulic pressure.

During anti-lock operation (hard brake application), a series of rapid pulsations (caused by the fluctuating of the modulator valve) may be felt at the brake pedal. These pulsations, in conjunction with a "clicking" or "buzzing" noise, are considered normal during anti-lock operation and will cease when normal braking is resumed or vehicle comes to a complete stop.