K072339 | Genuine Bendix® RV-1 Pressure Reducing Valve

1. Compatible System Applications

The Bendix® ATR-1 (Antilock Traction Relay) valve is an essential component of a heavy-duty commercial vehicle's air brake safety system. It combines a standard air brake relay valve with a traction control solenoid. It integrates directly into:

• ABS / ATC Systems: Works alongside the Electronic Control Unit (ECU) to manage Automatic Traction Control (ATC). When the system detects drive-wheel spin on slippery surfaces (like ice or mud), this valve automatically applies a controlled amount of brake pressure to the spinning wheel to transfer torque to the wheel with traction.

2. Common Vehicle Types

This is a universal Class 8 commercial vehicle component rather than a single-model part. It is widely found on:

• Semi-Trucks / Tractors: Freightliner, Kenworth, Peterbilt, International, Mack, and Volvo trucks equipped with active traction control.

• Commercial Transit Buses: Heavy-duty transit buses and motor coaches operating in regions prone to inclement weather.

Core Functions

• Normal Relay Function: During standard driving, it functions exactly like a regular rear-axle relay valve. When you press the brake pedal, it instantly routes high-pressure air from the primary reservoirs directly to the rear brake chambers to stop the truck.

• Automatic Traction Control (ATC): If the vehicle’s ABS computer senses that one of the rear drive wheels is slipping on ice, snow, or mud at speeds under 25 mph, it sends an electrical signal to this valve’s 2-pin solenoid. The valve then automatically applies precise air pressure only to the spinning wheel. This forces the vehicle's differential to transfer mechanical torque over to the stationary wheel that actually has grip, helping the truck pull away safely.

• "4 PSI DIFF" (Crack Pressure): The label dictates a 4 PSI crack differential. This means it takes exactly 4 PSI of air pressure to overcome internal mechanical resistance, open the inlet valve, and begin delivering air to the brakes.

1. Constant Air Exhaust Leakage (Audible Hissing)

If you hear a steady stream of air escaping from the exhaust port at the bottom of the valve when the brakes are released, the internal rubber seals or inlet/exhaust seat have deteriorated. A leak while the brakes are applied indicates a ruptured internal diaphragm.

2. ATC / ABS Dash Warning Lights Illuminated

The ATR-1 features an integrated electronic solenoid. If the internal coil shorts out, develops high resistance, or the electrical pins corrode, the ABS Electronic Control Unit (ECU) will immediately detect the circuit fault and illuminate the ATC (Automatic Traction Control) or ABS light on the dashboard.

3. Sluggish Brake Application or Slow Release

A failing relay valve may fail to rapidly route air to the chambers or refuse to exhaust it quickly when you lift off the pedal. If you notice a distinct delay between pressing the pedal and feeling the brakes engage (or if the rear brakes seem to drag and release slowly), the internal piston or spool is sticking.

4. Loss of Traction Control on Slippery Surfaces

If the mechanical double check valve or the electronic solenoid inside the top cover jams, the ATC system will fail to function. When pulling away on ice or mud, the truck will simply spin one wheel freely without the valve pulsing air to grab the spinning side and transfer torque.

5. Wheel Lockup or Uneven Rear Braking

If the valve's internal mechanism sticks or fails to balance air pressure properly, it can cause the rear brakes on that axle to lock up prematurely or apply unevenly compared to the rest of the truck, leading to dangerous skidding.