A train horn system for a truck is a high-decibel air horn kit designed to produce sound levels far exceeding standard vehicle horns. People typically install these systems for increased road visibility, safety, or novelty. Given the intense sound output, often reaching 150 decibels or more, proper safety precautions are necessary. Always wear adequate hearing protection when testing the system to prevent damage. Installation requires careful planning to maintain the vehicle’s integrity and electrical system.
Legal Considerations and System Components
Before beginning any physical work, verify all local and state regulations concerning auxiliary air horns. While federal law dictates manufacturing standards for horns used on railways, state and municipal laws govern their decibel limits and permissible use on public roads. Many jurisdictions impose maximum sound levels, often around 100 to 110 decibels, and restrict the use of horns that mimic emergency or train sounds. Check city and county ordinances to avoid potential fines or required removal of the system.
A standard train horn kit consists of several interconnected components. The core parts include the horns, an air compressor that pressurizes the system, and a storage tank to hold the compressed air. A pressure switch automatically regulates the compressor, maintaining consistent tank pressure, typically between 120 and 150 pounds per square inch (PSI). The system is completed by a solenoid valve, a wiring harness with a relay, and air line tubing, which control the release of air to the horns when activated.
Mounting the Compressor, Tank, and Horns
The physical installation begins by selecting appropriate and secure mounting locations for the large components, which is a significant factor in the system’s longevity. Suitable areas are typically underneath the truck bed, inside the frame rails, or in protected sections of the engine bay. These locations must offer protection from excessive heat, road debris, and water spray, which can significantly degrade the compressor and tank materials over time.
Securing the air tank and compressor requires a stable, vibration-free surface to prevent stress fractures and noise during operation. If a suitable factory mounting point is unavailable, you may need to drill new holes into the vehicle’s frame or crossmembers. When drilling into the metal frame, it is imperative to use a pilot bit and then a step bit to achieve the correct diameter. Immediately apply rust-proofing paint or primer to the exposed metal edges to prevent corrosion from compromising the structural integrity of the truck frame.
The air compressor generates heat and should be mounted with sufficient airflow for cooling. It must be oriented to ensure the air intake filter is protected from moisture and dirt, which can quickly damage the internal piston and cylinder components. Mounting the compressor vertically with the head facing up is often recommended to minimize the risk of oil or moisture buildup inside the unit.
The horns must be positioned to maximize sound projection while remaining shielded from direct exposure to water and road grime. Mounting them facing forward or slightly downward, perhaps behind the bumper or grille, helps direct the sound effectively. Ensuring the horn bells are angled slightly downward prevents water from pooling inside the trumpets, which could muffle the sound or freeze and damage the internal diaphragms during cold weather. Using robust, corrosion-resistant hardware, such as grade 8 bolts and lock washers, ensures the components remain secure despite constant road vibration.
Connecting the components requires careful measurement to ensure the air lines run without sharp bends or kinks. The placement of the tank should minimize the total length of the air line required to reach both the compressor and the horns. This placement reduces pressure drop across the system and ensures a faster, more consistent blast when the solenoid is activated.
Wiring and Air Line Connections
The final stage involves connecting the electrical and pneumatic systems to make the horn operational. Before touching any electrical wires, disconnect the vehicle’s negative battery terminal to eliminate the risk of short circuits and electrical system damage. The air compressor requires a dedicated, high-amperage electrical circuit due to its significant current draw, which can range from 20 to 40 amperes depending on the unit size.
The compressor must be wired using heavy gauge wire, typically 10-gauge or 8-gauge, running directly to the battery’s positive terminal through a high-capacity in-line fuse. This fuse protects the wiring from overheating and fire should the motor lock up or short circuit. A relay is incorporated into this circuit, allowing a low-voltage signal from the pressure switch to safely switch the high-amperage current needed for the compressor.
The pressure switch is wired into this relay circuit, acting as an automatic on/off switch for the compressor motor. When the tank pressure drops below the minimum threshold, the switch closes, powering the compressor. When the maximum pressure is reached, the switch opens, turning the compressor off. This maintains optimal system pressure and extends the compressor’s lifespan by preventing unnecessary cycling.
The solenoid valve, which controls the blast of air to the horns, requires a separate, low-amperage circuit. This solenoid is typically connected to a toggle switch inside the cab, which may be wired to override the truck’s existing horn button. This setup allows the driver to choose between the standard horn and the train horn. The wiring for the solenoid is much thinner, often 18-gauge, as it only needs to activate the valve mechanism.
On the pneumatic side, the air lines must be routed carefully to prevent chafing or exposure to hot engine parts, which can melt the plastic tubing. All connections, especially those leading into the air tank and the solenoid valve, must be made using appropriate thread sealant, such as polytetrafluoroethylene (PTFE) tape. Applying sealant ensures an airtight connection that prevents pressure leaks, which would otherwise cause the compressor to cycle constantly and eventually burn out. Once all connections are complete, the system should be tested by charging the tank and checking all fittings for audible leaks or using a soapy water solution to identify bubbles.