Installation Guide: Maximus Train Horn Kits

Before Using for the First Time:

After your kit has been installed, turn on the air pump and allow it to fill the tank until the pressure switch automatically turns the pump off.  Now you can test your horn!  Remember, the air compressor is not designed for continuous usage. The air pump needs time to cool down between horn blasts. If you plan on using the horn every couple of minutes, you need to seriously consider purchasing a very large air tank.

General Operation:

Power from the toggle switch to your air pump should only be turned on after you have honked the horn a couple of times. The compressor does have an automatic shut off pressure switch, but should that switch fail or a leak arise, the pump will run continuously and will drain your battery or cause premature failure of your pump.

Remember to turn the toggle switch on before each use, let the pump run until the pressure switch cycles off your pump, and then turn off the toggle switch.

NOTE: We recommended you hire a certified mechanic to install your train horn kit. Do not install or operate your kit without consulting a certified mechanic.

Relay Installation:

All Kits require a Relay. Relay Terminal numbers are on the bottom of the relay which correlate to the wiring diagram. You must unplug the connector to see the numbers. 

WARNING: Always disconnect the vehicle's battery prior to performing any of the following steps.

Click Here to Open Wiring Diagram in New Tab
Wiring Diagram, Installation Guide

Toggle Switch:

The included Toggle switch is for the air pump which prevents the pump from draining the automobile’s battery. Most Customers choose to activate their horn using the vehicle's stock horn button.  A second toggle or push button switch will be required if you prefer a separate button to activate the horn which is not included in the kit.

Air Pump Installation:

The Air Pump should be installed in a location that will not be subjected to the weather elements such as snow, rain or extreme heat such as heat within the engine compartment. Optimal installation locations are under or behind seats, in the trunk, in a tool box or spare tire area.

Pump Behind Seat Pump Under Seat

Air Tank Installation:

The air tank can be mounted anywhere you can fit the tank: Under your vehicle, in the bed of your vehicle, or inside your vehicle will work.

Note: In the event that you have a slight leak from the tank, DO NOT Tighten the gauge, fittings or pressure switch as this could strip the treading. Simply remove the leaking part and apply JBWeld to the threads. Tighten the leaking part just slightly past HAND TIGHTEN to ensure the threads do not strip. 

WARNING: Do not mount a plastic tank or plastic components in close proximity to exhaust and/or heat producing vehicle components.

Tank Installation

Horn Assembly Installation:

The horn is very durable and can be located on top, under the vehicle or under the hood. After installing the horns on the vehicle, connect the 1/4 in. Poly tubing from the Solenoid to the tank. A quick connect 1/4 in. adapter was included in the hardware which replaces the existing 1/2 in. connector on the solenoid.

NOTE: To prevent damage to the diaphragms caused by road debris, install the horns facing the rear, upward or to the side of the vehicle. This decreases the chance of debris collecting on the diaphragms.

Horn Under Vehicle Horn Installation, Under 2

Adjustable Pressure Switch:

NOTE: The center prong is removed by the manufacturer to prevent damage caused by not wiring correctly.

WARNING: Before adjusting the pressure switch, the air tank needs to be emptied. The 5/64 Hex Allen wrench is required to adjust the switch. Remove Plug from center of switch by unscrewing.  Do not adjust your pressure switch above 125psi.

Pressure Switch Installation Guide Adjustable Pressue Switch


If your horns begin to sound muffled and no air leaks can be found, you most likely need to clean your diaphragms. To do so, unscrew the back plates on each trumpet. Using a razor blade, gently cut the silicone sealing the back plate and remove the diaphragm taking care not to drop it. Gently clean the diaphragm with soap, water and a scouring pad. Reapply silicone and screw the backing plate and diaphragm onto each trumpet. Clean diaphragms once every 12 months to ensure sustained use.


Product Categories, train horns for trucks

Product Catalog, train horns for cars
        *Lower 48 States Only

Train Horn Kit News

Train Horn Kits wants to hear from you!  Send us your videos, pictures or thoughts and we'll add them to the website.

Learning Center