Description

Overview

The Sealco relay valve 4 port provides reliable service brake control for heavy trailers that need fast, balanced air delivery to multiple brake chambers. In normal operation, the valve relays air from the trailer reservoir to four delivery ports when it receives a control signal from the foot brake valve. As a result, brake response stays consistent across the axle group and reduces lag compared with long service lines from the tractor. With its compact body and proven Sealco design, this relay valve suits operators who want straightforward replacement of worn or obsolete trailer valves without redesigning the plumbing.

Features

• Firstly, four 3/8 NPT delivery ports allow the Sealco relay valve 4 port to feed multiple spring or service brake chambers on a trailer axle group.
• Additionally, a 3/8 NPT auxiliary supply port and 3/8 NPT control port simplify routing from existing trailer reservoirs and service lines.
• Furthermore, the 3/4 NPT reservoir port supports high flow rates so the valve can recharge the circuit quickly between brake applications.
• Finally, a nominal 4.5psi crack pressure helps balance response time with stable control, which supports consistent trailer braking performance.

Specifications and Materials

This Sealco relay valve 4 port configuration uses a 3/8 NPT auxiliary supply port, a 3/8 NPT control port and a 3/4 NPT reservoir port feeding four 3/8 NPT delivery outlets. Consequently, it aligns closely with common trailer air brake layouts and makes retrofitting easier when replacing older service relay valves with similar porting. The 4.5psi crack pressure allows the valve to open with a low signal from the foot brake valve while still maintaining predictable timing between tractor and trailer brakes.

Part number: AB8395.

Internal construction follows the Sealco service relay valve family that is widely used on highway trailers, with a metal body designed for harsh transport environments and rebuildable internals where repair kits are available. In addition, the relay valve body is compact enough for mounting near the trailer reservoir or axle group, which supports short line runs and reduced pressure loss. For background on Sealco relay valve coding and crack pressures, see this manufacturer technical guide.

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. 110143, RV045, LOV4, 110451.

Compliance and Safety

Fleet operators typically select this style of relay valve for trailers that must comply with modern air brake regulations covering service brake timing and stability. When technicians install the valve as part of a correctly engineered dual line system, it helps maintain even braking across the axle group and supports stable stops. In addition, workshops should always isolate the air supply, exhaust system pressure, wear appropriate eye protection and perform a full leak and function test before returning the trailer to service.

Trailer Applications

This Sealco relay valve 4 port suits general freight trailers, tippers, tankers and other heavy vehicle combinations that rely on multiple brake chambers per axle group. Technicians usually mount the valve close to the trailer reservoir or cross member near the axles so delivery lines remain short and responsive. Moreover, the standard NPT port sizes and four outlet layout mean it can replace many existing service relay valves when matched against the correct cross-reference numbers and plumbing orientation.

Cross-reference and Suitability

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

Before final selection, technicians should compare the existing valve tag and port layout with the listed cross-reference numbers and confirm suitability against workshop documentation.

Why Choose ICS Trailers

ICS Trailers focuses on practical information and proven brands so buyers can match relay valves to real trailer applications with confidence. Our team works with heavy transport operators every day, which helps us select air brake components that support uptime and straightforward servicing. When you need compatible service valves, we aim to provide clear specifications and responsive local support to keep trailers working safely on the road.

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