WILLIAMS CONTROLS 118588 WM778A Pressure Protection Valve

Manufacturer

WILLIAMS CONTROLS

Features & Benefits

• Automatically closes to protect primary air pressure when auxiliary demand increases
• Recloses at approximately 70 PSI to preserve braking system recovery
• Uses a normally closed design suited for primary-to-auxiliary air supply layouts
• Accepts inlet filtration to reduce contaminant entry into the air circuit
• Replaces WM778-series valves without requiring system reconfiguration

Williams Controls Air Brake Pressure Protection Valve

Protect your primary air system from accessory-related pressure loss with the Williams Controls Air Brake Pressure Protection Valve. Commonly used when auxiliary systems are supplied from a primary air circuit, this normally closed valve is designed to isolate non-essential air consumers before they compromise braking performance. As system pressure drops, the valve automatically shuts off airflow to accessories such as seats, horns, or secondary devices, then recloses at a nominal 70 PSI to preserve air for braking recovery. Built for real-world truck environments, the valve uses a durable metal body rather than lightweight plastic, reducing the risk of cracking or seepage over time. The Williams Controls 118588, part of the WM778 series, installs inline as a direct replacement and helps maintain stable brake system pressure in vocational and on-highway applications.