Install instructions

Train Horn Install Instructions

I wrote this article because of my interest in having Train horn on my truck and the lack of comprehensive information on such a project. There are posts wandering about the Internet on the results of someone's mod with a picture here and there but nothing that answered the many questions that I had nor anything that approximated a "how to guide". Even the company that supplied my kit offered little useful advice. I do apologize for the pictures since I wrote the article after the horns were installed so bear with me in the photographic aesthetics area.  

Secondly let me state that this installation is about air horns. Those used in industrial applications. You know the big boys that use serious air. Not the plastic trumpets driven by those Coke can compressors.

Further there are many variations of how to do things and I cannot cover every angle. I will state what worked for me.

Let’s begin.

The Cost

The installation of these horns is expensive. Plan on spending several hundred to well over a thousand when all is said and done. There are places costs can be shaved and places it shouldn’t. More on that later.

The Parts


I installed Nathan Airchime K3LA horns on my Chevy Trailblazer These train horns cost a bit over $500. You can find train horns, marine horns, and such in many places. I have watched auctions and they all end at $500 to $1000 for a set of train horns. What do the letters and numbers for the horn mean? The K is the series of horn. Airchime made M, P and K series that I know about. I am a serious train buff so if you want more information “track” down a train enthusiast site. There’s a couple in the Yahoo Groups area. They also sell horns there. The bonus buying there is the knowledge and expertise from those with a passion for trains. The “3” means three trumpets or bells. Each is tuned to a different note. Airchime continues to manufacture K series and other horns for industrial applications such as mining. Those horns have a coverage of up to 6 kilometers and can put out 147 db at 1 meter.

The M is an older series, has a mellower sound is rare and thus more costly. The K series is what you hear on modern locomotives. It is about the loudest horn out there putting out a teeth rattling 114 decibels at 100 feet. But volume has its price. They use lots of air. That is why I chose the K series. It was Nathan’s most efficient horn for air usage and is more than loud enough for me. Efficiency is important to us because we are limited on air supply.

I also paid more because I bought from a business that refurbishes and sells these horns.

Marine horns are another option. Buy what you like and will work for you. Think about mounting and function in making a decision.

That plate supporting the horns is ½ inch thick steel.

Air Tanks:

The louder the horn and the longer you blast the more air is required. A small tank just won’t maintain the sound volume for long. A few blasts and your done. The larger the tank the more time you have and the longer the sound can be sustained. I strongly recommend 5 to 6 gallons minimal. I installed twin 6-gallon tanks on the Trailblazer Even with the K3’s a short blast drops pressure 5 to 10 psig. I bought my tanks, which came in a kit from But this included all hoses, fittings, pressure switch, inlet filter and compressor. Most everything is top shelf. I had problems with the fittings, which, I will mention later.

If you opt to shop around for a tank ensure it is in good shape, you know its history and it is pressure tested. Some machine shops will pressure test the tanks for you. Avoid anything that was picked up from a junkyard or other dubious origin. These horns operate around the 120-to150-psig range or higher and are going to be mounted on your vehicle possibly near vital lines. Don’t go cheap here. Try to get tanks with a drain valve. Water will accumulate in the tank and this valve will make it much easier to get rid of it.

The Compressor:

If you’re not going the compressed bottle route then you have to put back in what you take out. For an occasional horn blaster like me the Viar compressor that came with the kits does fine. The horns can easily out run its low output, which is why I installed two 6-gallon tanks. However sounded horns like these is impressive. You only have to do it once. Trust me you won’t want to do it a lot. There are much higher SCFM compressors out there made by manufactures such as Oasis. These things can operate air tools and could drive the horns directly but probably not at their recommended pressure. Also plan to fork out $1000+ for one of these. If you don’t plan to run tools off the truck or have no need for such a beast the money can be better spent elsewhere. Like other modifications.

The intake for the compressor must be routed away from water. Mine is piped into the cab to take advantaged of dry air-conditioned air in Virginia’s wet and humid weather.

If you plan to install the compressor outside of the cab ensure it is spray and drip tight.

Pressure switch:

Unless you want to manually turn the compressor on and off while staring at a gauge then you need one of these. In conjunction with a relay it cycles the compressor to maintain proper tank pressure.

This part is critical to safe operation of the system. The setpoint for the switch should not only be based on the horn’s operation pressure but also should complement the compressor’s output. That is, the switch should not be rated outside of the compressors range or safe operating pressure for the tanks. Mine cycles from 115 psig to 140.


Get the best quality you can buy. Buy new if possible. These lines are exposed to weather and often run beneath the vehicle subjecting them to various road hazards as well as vibration and rubbing. Ensure all are rated for the pressure.

The Valve:

You need a way to sound the horn. Train engineers use a manual valve. The most common goes by the name of Graham White but that is for the purist. A manual valve simplifies the installation, provides a positive means to isolate the horn and allows variation of tone. It also means you have to find a way to run lines in and out of the vehicle as well finding a way to mount this valve. They aren’t small or cheap. The prices I have seen are 100 to $150 for new or near new.

I use a fast acting SOV wired to a switch mounted on the cover below the steering wheel. The upside is a much easier time running wires vice hoses, it’s cheaper at about $40 for the SOV and the sound is instantaneous. The down side is more electrical connections, water entrainment from the tanks and that all such valves have temperature limits. Mine is a GC 12 SOV. I contacted the company and they stated that although the valve is rated for freezing temperatures it could flow liquid O2 but that not recommended. I operate hundreds of these style valves at work and although I can’t remember any failing due to temperature but it can happen. Having a valve supplying a horn stick open would be ugly. It is recommended that these valves be installed in the engine compartment for the heat.

The gauge:

You need to know what is going on so install a gauge. For convenience I ran a line inside the cab and have the gauge sitting below the dash and above the transmission hump. Protect this line wherever it enters the truck from rubbing. If this thing ruptures I hope your seats are vinyl because you will be cleaning them when you get back home


Self explanatory. I strongly urge some mean of deenergizing the system. I have a momentary switch for the horn and another, which interrupts power to the pressure circuit. This prevents the compressor from starting when I don’t want it to, like in the middle of a cold night or when the engine is cranking. An illuminated switch was used here so I am reminded of the system’s status. The horn switch is the black one to the right in the photograph below. Note the fused power supply.

These are the basic parts. Now on to the installation.

After deciding on the type of horns deciding on where they should go is the next step. Do you want the horns hidden or out for all to see? Because of their size and because I wanted them visible I mounted my horns on my forward rack. I have sliding racks on the bed rails so it was a logical place. I left enough hose coiled between the bed liner and the side to allow for a few feet of rearward movement of the rack without removing the horns. Because of the design of the racks should removal of the horns be required I need only undo two bolts. Mine are also train horns and quite honestly when is the last time you a train with its horns beneath the locomotive?

Benefits of mounting topside include visibility for aesthetics, protection from road debris, not having to deal with an already crowded engine bay and less lines near hot or rotating components. The dollar investment demands thought in location.

The downside of topside mounting? They are visible and many know their worth, which might attract the wrong attention. Also due to their weight they need a sturdy mount and if you don’t have racks then you must fabricate some sort of base plate. With the heavier horns sheet metal is not an option for support.

Mounting location is also dictated by truck style. Look closely at what you have. Just make sure the horns are firmly in place, out of harm’s way and if possible tilted slightly downward to promote drainage. You are responsible for anything that falls off your truck and one of these bad boys bouncing down the road is going to do damage.

Grill mounting, front bumper or under carriage is popular. It’s your choice.

Where to put the tank :

Probably the easiest place is in the bed, inside of a toolbox. There the tanks and compressor are protected, accessible for maintenance and inspection and secure. Make sure that the compressor is not touching the tank and has space around it to allow for air circulation. Keep hoses clear of the compressor and sharp edges.

I chose to install my tanks and compressor beneath the cab next to the frame rail. Here’s where a knowledgeable salesman paid off. He shipped tanks that would fit between the frame rails of my TRAILBLAZER

Beside the frame rail is a popular and generally a logical choice for the tanks.

mounted the tanks, compressor and relay on a skid I fabricated from square metal stock and thick sheet metal. All found at the local home improvement store. This allowed me to do much of the assembly in the comfort of the garage at my workbench. Doing this also allowed me to do a temporary assemble of all parts, pressure test the tanks and sound the horns. That way I knew everything worked before crawling under the truck.

Pressure check all you can off the truck. It’s just easier. Air leaks will cause excessive cycling of the compressor, which causes premature failure and may void the warranty. It will for the Viar.

The smaller the tank capacity the faster the tank will depressurize for any given size leak and horn usage. This is another reason I went with twin tanks. It means the horn is more likely to be ready when I jump in. It takes my compressor about 3 minutes to raise the tanks from 0 to 200 psig.

Fancy quick disconnect fittings came with my kit but I prefer standard compression fittings. They’re cheap, familiar and easily found. Three of the quick disconnect fitting in my kit failed. One completely separated around 15 psig. Imagine that at 150 psig!

Make sure the nuts can’t back off. Use a medium strength thread locker or whatever you like. I prefer nylon inserts. Don’t use lock washers.

Try to keep the tank out of harms way. Keep the length of the discharge hose --" the hose from the valve to the horn short but allow for movement and body flex. Remember this hose is only under pressure during horn operations so danger from whip is minimal. Keeping the hose shorter will make for less sound time delay. I purposely left a few feet coiled between the bed liner and truck to allow movement of the racks as mentioned earlier but also to delay the sound ever so slightly. I am not only after the volume but am also trying to better mimic the sound of a locomotive. The extra hose acts as a surge volume allowing the horns to sort of wind up like they would when an engineer throttles open the manual valve in his cab. We’ve all heard the low to high pitch of a train horn as it approaches a crossing. I have another SOV to be installed in the future in parallel with the current one. This second valve will have a throttled ball valve in line with it. Wired to the second contact on the current momentary switch I will be able to sound a sustained low blast and then switch to full volume. As mentioned the larger the tanks then the longer the note and the better the sound recreation.

The Compressor:

The compressor can go anywhere you can fit it. It needs to be able to cool itself and be out of danger’s way. The compressor’s intake must draw on clean and preferably dry air. Unless you live in the desert and never leave the garage this mean routing an intake line away from moisture and dirt.

Since the cab is climate controlled I routed my intake there. The Viar came with a filter and housing that fits on the end on the suction tubing. Find a knockout somewhere on the fire wall and feed the tubing through. I routed mine through the same knock out as the gauge line. The place I found that works is on the firewall below the glove box to the far right. Watch for sharp edges that could do damage via vibration. My filter is tucked high above the front passenger’s feet. I rarely have someone with me so this works out. I placed it so someone would have to really kick around to hit it.

The compressor can draw lots of current. Pull power directly from the battery --" not from any existing circuit. Route it through a relay controlled by the pressure switch. Use the largest wire you can and keep the run short to mitigate the voltage drop. I found the wire I needed at Lowes. The lead for my compressor was supplied. It is without question the thickest wire I have ever seen on a vehicle. It is almost the size of a fuel line. It is as thick as any of my house wires. Any significant voltage drop must be avoided. You’ll smoke the compressor and/or blow fuses.

The valve:

As mentioned earlier if it’s an SOV then it can be mounted anywhere. Try to keep the orientation correct. The colder the climate the closer to a heat source it needs to be mounted. Another option is to buy an SOV rated for your temperature. Again watch the run to protect it from vibration and missiles.

If you want to go the manual route more power to you. You’ll have to figure out the best way to feed the air lines into your truck. You’ll also want the valve somewhere near the driver’s armrest.

The SOV is also where water intrusion is a concern. Contamination can cause these valves not to seat. At best this will result in system leakage. At worst a horn with no means to turn OFF! I can’t stress it enough. Keep the system clean. Use clean, dry and preferably filtered air. Drain the tanks periodically.

Since an SOV is an electrical/pneumatic/mechanical device it can and will eventually fail. The odds and time of failure will greatly depend on its quality, the climate and the care you take with wiring and installation. As always you get what you pay for and reap whatever level of effort goes into the job. Invest in both wisely.

Once everything is hooked up do a slow pressurization. If using the installed compressor ensure the engine is running prior to running the compressor. I have a normal 3/8 th female fitting installed on the rear most tank pointed to the tail end. This comes in handy for allowing tie in with my shop compressor and for easy depressurization. If you do install such a fitting make sure it faces towards the rear and cover it if possible to eliminate catching dirt and water that could interfere with connecting or enter the system.

At about 20 psig or so stop the pressurization and do a leak test. A weak soap solution will do or you can buy leak detection liquids. Take your time and wait for the bubbles. Tighten the leaking fitting and move on. Make small adjustments maybe 1/16 th of a turn at a time. 100% leak tight is probably not going to happen but get as close as possible. You should not be able to see the gage move nor hear any air escaping. Teflon tape works well but never use any on the intake side of the compressor. If you do use the tape use it sparingly. The horns diaphragms have a small orifice, which could become fouled by tape shreds that became dislodged.

Keep after the leaks. When satisfied start the engine and allow the compressor to bring the system up to operating pressure. Keep an eye on the gage to ensure the compressor stops when it should. When the compressor cuts off do another leak check and tighten fittings as necessary. Be careful hoses aren’t twisted as you tighten.

Ensure all are clear or warned, get inside, roll up all windows and sound the horn. Do a quick blast.

If all has gone well to this point drive the truck a short distance and check that all is as it should be. Drive a mile or so and do another check. Look closely at the hardware.

Dos and Don’ts:

Don’t sound these horns near those without ear protection. I can’t overstress this point. The driver you’re blasting is inside an insulated car and probably farther away from the horn than you so what he hears is going to be quieter than what you hear. My horns, even being mounted topside, are not very loud with my windows closed but are ear splitting loud to those outside on two feet. In other words you may piss off a lot of innocent pedestrians and the guy in front of you with his cell phone and music may not even notice. At close range you can cause damage to someone’s eardrum. Once I forgot I had both passenger side windows down about 6 inches when I sounded the horns. For the next couple of hours hearing in my right ear was dulled. As mention above these things put out 100+ decibels at 100 feet. Think of these horns as acoustic howitzers. Pause to think before you blast.

Don’t allow any lines to rub or dangle.

Don’t pull compressor power from an existing circuit.

Don’t allow excessive leakage. It will kill the compressor.

Don’t mount any parts near rotating components or high heat sources. This goes especially for pressurized lines.

Avoid joining dissimilar metals if possible. Having different metals touch causes electrolytic corrosion. Add moisture and you have basically made a weak battery.

Do use nonmetallic washers or gaskets between the component or mount and the truck body. This will help dampen vibration and prevent metal-to-metal contact and thus electrolytic corrosion.

Don’t overwork the metal if you do fashion brackets or mounts. This creates stress that will relieve itself through accelerated corrosion and cracking.

All brackets here were fashioned on my anvil from steel stock. Rubber washers are fitted at all bracket to skid and bracket to body interfaces to dampen vibration and prevent metal-to-metal contact.

Next time Quote ur F*n Source!

My buddy wrote that and it was orginally off of a german website

haha… that’s a good article though.


good article

One little finger get blown off and everybody tripping

Its a good write up

Reg Robinson dosent sount too german to me…

The cool part:

By re-Posting something that’s already published on the internet on another horn site, Google crawls our page and sees we have duplicate content actually “Plagiarized” word for word without sources and google’s rating system for page relevance known as “page rank” scores our site trainhornforums as repetitive B.S. which in turn hurts our search ranking. That’s right, by reposting that duplicate content it actually Hurts our website. Please anyone that wants to post only post original content. I think it’s like every 9th word needs to be different or something… Jeremy. You could TOTALLY help us all out and re-write that article in your own words, it would help out the forum BIG TIME! just read everything a couple times, and re-write it in your own words. It would mean a lot ot me, anyone that wants to do that about any horn info you have, post it all up, that’s “content” which enriches the site and will make the forums even bigger when people search for this stuff on Google, we will come up and offer an entire community and resource on the topic.
-Heller Out!