Description

Overview

The Pacific R-12P pilot relay valve is a zero differential air brake pilot relay valve for trailers and converter dollies. It reinforces the control signal along long combinations so distant trailer axles see a balanced service brake pressure. As a result, multi trailer sets gain more even braking and better stability, especially during light applications where small pressure changes matter.

Features

• 0 psi crack and differential design that relays light control inputs quickly so rear trailer chambers respond without delay.
• Two 1/2″ NPT supply ports and four 3/8″ NPT delivery ports that give flexible plumbing options on multi axle trailers.
• Pilot operated relay layout that boosts the control signal and helps keep trailer brake pressure closely matched to the lead vehicle.
• Air brake pilot relay valve pattern that suits long wheel base trailers and converter dollies where response time is critical.

Specifications and Materials

This Pacific R-12P pilot relay valve follows the common Bendix style layout with two 1/2″ NPT supply ports, four 3/8″ NPT delivery ports and a 1/4″ NPT control port plus a dedicated exhaust outlet. The 0 PSI crack pressure means the valve begins relaying air as soon as the control pressure rises off zero, so the delivery pressure can follow the control pressure closely along the brake train.

During a service brake apply, control pressure acts on the relay section and opens the inlet so supply air flows to the delivery ports until delivery pressure balances the control signal. During release, the relay section closes the inlet and opens the exhaust path so the trailer brake chambers vent quickly and return to free rolling. Construction typically uses a cast or machined aluminium body with corrosion resistant internal parts suitable for heavy vehicle air systems.

Part number: AB8475P.

You can review a similar R-12P valve layout and operation in this manufacturer technical guide where Bendix explains the trailer pilot relay family in more detail.

Compatibility and Fitment

This cross-reference listing means this valve is a suitable replacement for the part numbers and applications shown. Some changes in air line plumbing may be required. 109264, 065476, 109001, 109002, 109424, 109446, 65476.

Compliance and Safety

Before you work on any air brake pilot relay valve, park the vehicle on level ground, chock the wheels and drain the air system fully. Next, label every hose and port so you can refit the lines to the correct locations on the new Pacific R-12P pilot relay valve. After installation, recharge the system and check each joint with a suitable leak detection solution. If any axle shows slow apply or slow release, stop the job and ask a heavy vehicle brake specialist to confirm the circuit is correct before the trailer goes back on the road.

Trailer Applications

Workshops use the Pacific R-12P pilot relay valve on long wheel base trailers, towing trailers and converter dollies in double or triple combinations. Installers usually mount the valve close to the service relay valve or reservoir so it can boost the control signal near the axles. In addition, the valve can act as a slave to a trailer ABS system on remote axles that need a matching pressure response. Always follow the original trailer brake schematic or an approved modification drawing when choosing the final mounting point and plumbing layout.

Cross-reference and Suitability

This part cross-references to or suits the following equivalent part numbers and compatible alternatives:

Use this list to confirm the existing valve pattern on the trailer and to check that a Pacific R-12P pilot relay valve is an appropriate replacement.

Why Choose ICS Trailers

ICS Trailers focuses on air brake parts for heavy trailers, so we match pilot relay valves to real fleet conditions instead of light commercial vehicles. Our team checks port layouts, crack pressure and common cross references carefully, which helps you select replacements with confidence. In addition, we support workshops with practical product data so you can keep downtime low and maintain stable braking across complex multi trailer combinations.

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