The flow-control valve is...
The flow-control valve is between the pressurized air tank and the horns. It needed to be mounted in a secure location, so we used sheetmetal screws to attach it to the underside of the body. This valve only has two wires: one goes to ground, and one connects to the factory horn through the HornBlasters toggle switch.
Bolt-On Kit
For our project, we contacted HornBlasters, and after a quick talk, we were advised that its Conductor's Special package would fit the bill nicely. This kit includes everything you need to install it on any vehicle. It's a four-horn system that includes a 150-psi compressor and pressure switch as well as all the lines, wires, connectors, and in-cab controls to complete a first-class install. All you need to supply are basic handtools and your time.
Train Horn Laws
The use of any device this loud should be done with caution, and you should only use the train horn in case of an emergency-or to avoid an impending accident. The laws on the use of train horns vary from state to state, and even from town to town. In some areas, they are legal to own but illegal to use. So you should ask your police department about the local laws before finding yourself at the receiving end of a noise-violation ticket.
In Chattanooga, Tennessee, where the install was done, the sound of a train horn is very common. Some people are abusing the use of these horns, resulting in fines from the police. If you practice common sense and use the horn on an as-needed basis, you should be fine. For this truck, we used a toggle switch that allows the factory buttons to activate the stock Dodge horn or the HornBlasters kit when desired.
 After mounting all four horns,...  After mounting all four horns, we cut four equal-length pieces of air line and attached them to the horns and the manifold. (Make sure you tape the brass threads and completely bottom-out the compression fittings.) Then we cut a piece of air line long enough to connect the flow-control valve to the brass horn manifold. We made sure there were no kinks or sharp bends in the hose and avoided routing it too close to the exhaust. |  Using the supplied fuse connector,...  Using the supplied fuse connector, we attached the 12-volt lead to the battery and routed it to the pressure switch. We then connected the remaining wires to the pressure switch: one to ground, one to a 12-volt switched source, one to power the compressor, and one to ground. The compressor only needed one ground after these connections were made. |  We double-checked all the...  We double-checked all the air lines for correct tightness (the outer brass fitting needs to be bottomed-out against the compression fitting) and made sure all the fittings were wrapped with Teflon tape. This was a good time to make sure all the air lines and wires were safely routed. We used cable ties to secure them. |
 The system requires a solid...  The system requires a solid ground to the vehicle. We found a factory ground strap between the cab and body and used it to connect the flow-control valve ground as well as the compressor ground. |  When routing the new wires,...  When routing the new wires, wiring loom can be added to clean up the appearance and keep the factory look under the hood. It's also a good idea to protect any wires or air lines that could be exposed to vibration or rubbing against the vehicle. We covered all suspect lines with a plastic loom for this reason. We soldered everything and covered the connections with shrink wrap. |  Finally, we routed a wire...  Finally, we routed a wire from the stock horn through the firewall to the HornBlasters toggle switch we installed near the driver seat. Then, from the toggle switch, we ran a wire back to the flow-control valve. This will serve as the activation switch to allow us to use the stock horn button to fire the train horns. When the HornBlasters toggle switch is off, the stock horn is utilized. When armed, the factory horn and the train horns sound together. |