Description

Overview

The trailer air brake double check valve 1/4in ports is a DC-4 style valve used to feed one function from two air sources. It selects the higher pressure source so the protected circuit keeps working if one supply drops. As a result, it helps maintain control of key trailer functions when reservoir or supply pressure is uneven.

Features

• Trailer air brake double check valve 1/4in ports that selects the higher of two air supply pressures.
• Internal shuttle or disc that moves toward the lower pressure side and seals it off from the outlet.
• Three 1/4in NPT female ports, two inlets and one delivery, for compact plumbing in trailer systems.
• Recommended horizontal mounting of the shuttle section to promote consistent operation when pressure differences are small.

Specifications and Materials

This DC-4 model double check valve directs air from whichever of two sources is at the higher pressure into a common delivery line. It suits trailer air brake and auxiliary systems where a single circuit, such as a control valve or relay, must stay supplied even if one upstream feed drops away. The valve body has three 1/4in NPT female ports and uses an internal shuttle or disc to isolate the lower pressure side. Part number: AB8369. For wider technical background on DC-4 style double check valves see the Bendix manufacturer technical guide for DC-4 double check valves for broader reference on design and operation.
Technicians should mount the valve so the shuttle operates in a horizontal plane, which helps its movement remain smooth under light pressure differences.

Compatibility and Fitment

In typical use this trailer air brake double check valve 1/4in ports supplies air to a relay valve, modulator or other device from either of two control sources. It can also sit between primary and secondary circuits to feed whichever reservoir holds the higher pressure into a shared service. 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. 278615, 3081439, 1779P1005, 275858, 285543, 288334, 118914, 107928, S1177726, 6D3781, 2558147, M6001213, 350180, BW 278615, 2485247, 532187, GTA278615, 78037062, 86683301, KN25060, H278615m 31A1812, 335357, 81277, K29520004, 20396450000, 36Z1090D1, 36Z763, 13AV4000, S-16923, 724040012, 289547, N20954, 060-278615.

Compliance and Safety

Only trained personnel should work on air brake components and they must follow workshop procedures for isolating and draining the system. Before removing any double check valve, secure the vehicle and trailer with chocks or another approved method so it cannot move. After installation, technicians should soap test all joints, confirm the protected circuit receives air from the higher pressure source, and verify that both supply lines can independently feed the downstream device.

Trailer Applications

This valve suits semi trailers, B double sets and other heavy trailers that need a reliable way to select the higher of two air sources. For example, it can allow a trailer function to operate from either the foot control or a hand control, or from either of two reservoirs, without complex plumbing. Therefore installers should confirm the port labelling, follow OEM diagrams and keep the valve accessible for future testing and service.

Cross-reference and Suitability

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

Use this list to match fleet records and OEM documentation when confirming interchange between different supplier numbers.

Why Choose ICS Trailers

ICS Trailers specialise in heavy vehicle trailer parts, so you can source double check valves, relay valves and fittings from a focused supplier. Our range centres on proven air brake components that match common DC-4 style layouts, which helps reduce installation time and repeat faults. For related valves, fittings and protection hardware, browse Air Brake Parts at ICS Trailers today.