A Trailer control valve is used to regulate air pressure in a trailer. The valve is also called a retention valve. It works together with the auxiliary and service brake systems to control air pressure. It gets a signal to operate the valve when a pneumatic pressure is requested. When this signal is received, the retention valve 46 is closed. However, the signal from the pneumatic control circuit 26 cannot operate the trailer control valve 14. In such a case, the electrical control circuit 25 takes precedence.
Relay valve

The Relay valve for trailer control valve is a device that is used to synchronize the braking and air release systems of the trailer and the vehicle. The valve is a mechanical component that is analogous to a transistor in an electronic circuit. It is typically used to release the brakes of the trailer after pressing the release valve against a stop button. It is primarily used on trailers and vehicles that have automatic load sensing valves.

The Relay valve for trailer control valve is designed to provide the air brake system of the trailer with a predominance over the pressures of the towing vehicle. It works by pulling air from the trailer's air tanks and delivering it through the brake chambers over a distance of three to four feet. This short distance reduces brake lag and allows the spring brakes to apply in a split second after a driver releases the pedal.
Inlet valve

A trailer control valve uses a spring-loaded inlet valve that transmits pressure to the brake disc. The inlet valve connects to the reservoir air connection (port 2-1) on the trailer. The spring-loaded inlet valve is closed and a valve plate (the "presence" valve) guides the stem. The predominance valve and the valve plate are closed when the trailer vehicle is uncoupled.

A trailer control valve is a relatively complex and expensive construction component. The purpose of this valve is to prevent a failure of the trailer's electrical control circuit. The valve is often referred to as an inlet valve. The electrical control circuit is the primary source of power, and the pneumatic circuit is the backup. It functions reliably in all but the most severe conditions, and the valve is designed to be accessible to prevent accidents.
Retention valve

The Retention Valve for Trailer Control Valves is designed to limit the hold-off pressure applied to the spring brakes in the trailer. The device mounts in the trailer brake reservoir with a 3/4" pipe thread connection and comes with a safety cap. To adjust the hold-off pressure, the user must depress the valve release lever. A guide will be provided for adjusting the hold-off pressure. The valve must be installed in the correct position so that the spring brakes will not overheat.

A Retention Valve is a device used to hold back control pressure to prevent a failed electrical control circuit. This device is relatively expensive to install, but it is a vital safety device. If the electrical control circuit fails, the valve opens and releases the control piston. This process prevents a trailer from moving. It also prevents a sudden stop or stall by regulating brake pressure. As a result, this valve is an essential component in trailer control systems.
Functions

If you've ever used a trailer, you've likely heard about the functions of the trailer control valve. This device is a critical part of your trailer's electrical control system, and it functions to prevent failure of the circuit. It functions by introducing control air into a second chamber to keep the control piston mobile. It's connected to a pneumatic or electrical control circuit. When the pneumatic circuit is working, the valve assumes an open position, and when it fails, the valve closes.

The air supply line flows into the control chamber 89 from port 2-1. A control piston in the inlet allows air to flow through the port, which in turn directs it into the trailer's air tank. The port on the outlet side allows air to escape through a hole in the spindle. This air then flows into the trailer's brake chamber, where it applies pressure to the tires. This process ensures that the brakes are working at their maximum level.
Maintenance

Proper maintenance of the trailer control valve is crucial. The valve introduces control pressure into the brake line when it is in the brake position, so it must be kept bleed-free. The trailer control valve must also be properly installed with the vent facing downward. A few basic tips are outlined below. Follow them to keep the trailer control valve in good condition. After each inspection, lubricate the valve and adjust the predominance as necessary.

The trailer control valve is equipped with a pneumatic control circuit that closes and opens it when a brake pressure request is made by the electrical system. When a pneumatic control circuit is malfunctioning, it cannot operate the trailer control valve. The pneumatic control circuit, meanwhile, takes pr