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2004 Chevrolet Blazer ZR2





Onboard Air



Frigid Chicago winters, combined with too much time on the Internet, are a dangerous combination. What might seem like ridiculous thoughts in the glory days of summer turn into completely reasonable ideas when the temperature outside reads 4 degrees Fahrenheit. Such was the case one January day when I visited my favorite (and now defunct) website, ZR-2 USA, and discovered RancherMatt's train horn setup. RancherMatt is a gentleman from Upstate New York with a penchant for ear-splitting blasts from the innards of his 2002 Chevy S-10 ZR-2. While his post made me think this might be a necessary modification for my Blazer, the videos on Hornblasters.com made me know I had to have the horns.


The Hornblasters.com HB4H's are not just any horns. Remember that sound from a locomotive at a railroad crossing? These are the horns. They are powered by air pressure, which means their operation requires an air tank and an air compressor. Bouncing cars have been powered by air pressure for many years, which means plenty of tanks and compressors are available for all types of auto applications. It's just a matter of finding the right combination to power a set of unnecessarily loud horns.


Air tanks come in all shapes and sizes. I wanted at least 2 gallons, which is probably about the minimum for running a 4-horn set if you want any type of sustained blast. Auto-application compressors come in two general types: electric and engine-driven. Electric compressors seem to be the most common due to their size (tiny) and price (reasonable). Engine-driven compressors are mounted in line with the same serpentine belt that drives the alternator, air conditioner compressor, and water pump. They cost more and put additional load on the engine but produce large amounts of air - enough to power air tools. I decided to go with an electric compressor mainly because I didn't see myself needing huge air volumes and the compact size would be good for squeezing into small spaces. As with my sound project a few years ago, I wanted to preserve all possible interior space, keep expensive modifications out of sight, and mount that noisy compressor as far from earshot as possible.


RancherMatt had already demonstrated that the Hornblasters.com 4-horn setup could be squeezed between the radiator and the grill of a ZR-2. But where to put the air tank and compressor? RancherMatt mounted his inside the bed of his S-10. I had other ideas. Could the tank and compressor fit under the BlaZeR2? The short answer was yes, depending on the size of the tank. Here's what I had to work with:





This area is on the drivers side, opposite the muffler (we're looking toward the rear of the vehicle). It doesn't seem like much, but there's a solid 2 feet of space from front to rear and another 15 inches or so in width. My goal was to find a tank that wouldn't extend below the frame rail, so my options were somewhat limited. Fortunately, Viair had the right-sized application for this space, a 2.5 gallon tank with six 1/4-inch ports. Mounted on its side, the tank is no taller than the frame rail. Perfect.


Next question: where to put the compressor. Again, Viair makes a nice little 100% duty compressor so small it almost looks like a toy. Moisture resistance and horizontal mounting capabilities were an added bonus.


My master plan was falling into place. On went the computer, out came the credit card, and cool things began arriving at my home. For this project, I had the clear advantage of being the son of a farmer, with access to a heated shop, heaps of scrap iron, every tool known to man, and an advisor (Dad) willing to help keep me from destroying stuff (including myself). To do this job, at minimum you must have a drill press and some sort of metal cutting device that doesn't involve a $15 hacksaw. Anything less will frustrate you beyond belief (an air grinder works pretty well, too).


Both Hornblasters.com and Thorbros (formerly Suicide Doors) sell various HB4B four-horn packages complete with compressor and tank, but none had the exact combination I needed. The horns and Viair 380C compressor came from Suicide Doors, along with a Viair 110/150 pressure switch. I'll get to the installation schematics later, but the pressure switch tells the compressor to kick on when the air tank pressure drops below 110 PSI and to shut off when tank pressure reaches 150 PSI. The tank came from an eBay seller.



the project





A collection of interesting items.





Air compressor



Viair 380C compressor, complete with relay and intake hose and filter. The relay is unnecessary if you buy the Viair pressure switch, which has its own relay inside. The air line is for the compressor intake.



Bring on the horns



The Hornblasters kit included four horns, 20 feet of 5/16" air line, solenoid air valve and fittings.



Accessorizing



It's good to have a few accessories for projects like this one.





So now, the fun begins. The first task is understanding what has to happen to make these bad boys start scaring the pee out of unsuspecting individuals. For me, it would start with a push button to activate the solenoid that releases the compressed air into the horns. I didn't want the Blazer's horn to activate the solenoid because I don't feel like it gives me enough control - the auto horn is activated by pushing on the center of the steering wheel in no specific spot. With a separate button, I would always know exactly what (and where) to push.


When the horns sound for any length of time, pressure in the 2.5 gallon air tank drops quickly, so the air compressor will probably need to start compressing. That's where the pressure switch comes into play. It serves two purposes: a) senses when the air tank pressure drops below 110 PSI and b) tells the air compressor to switch on. Thus, the pressure switch needs to be connected to the air tank to sense the air pressure, and also connected in line with the main power wire going to the compressor (power is sourced directly from the battery). Inside the pressure switch is a relay which opens when the switch tells it to, sending power to the compressor until the switch senses 150 PSI in the air tank.

The pressure switch needs its own power source to work. This source can be from just about anything that's only giving it juice when the ignition is on. This serves as protection from the compressor kicking on when the vehicle isn't running and draining the battery. If the pressure switch isn't able to sense anything, it can't turn on the compressor. I went a step further and added an interior switch that would disable the horns altogether.

Connecting all of the components is a plastic-type air hose. The Hornblasters kit includes an odd-sized 5/16" outside diameter hose that is hard to locate elsewhere. Finding more of this line takes some heavy searching. An alternative would have been to use a more standard sized line such as 3/8", with separate 3/8" fittings.



Getting started





For my setup, here's what I bought in addition to the horn kit, air tank and compressor:

  1. Primary wire for the compressor - I used 10-gauge enough to handle the compressor's 16-amp load.
  2. In-line fuse for the compressor - I used a fused distribution block, which combined the compressor's 40-amp fuse with the fuses for my main amp and subwoofer amp.
  3. Miscellaneous smaller-gauge wire for the pressure switch, push button and horn disabling switch.
  4. 12v push button.
  5. 12v switch for disabling horns.
  6. Small-amp in line fuses and holders for the pressure switch lead wire and the horn disabling switch.
  7. Miscellaneous wire terminal connectors.
  8. Grommet for wires routed through firewall and inside the cab.
  9. Teflon pipe thread tape.
  10. 3/8" nylon tubing (to extend the air intake line on the compressor).
  11. 5/16" tube-to-1/8 inch pipe T-fitting (for pressure switch).
  12. Pair of 5/16" tube to 1/4-inch pipe connectors.
  13. Drain cock for air tank (1/4").
  14. 175 PSI pressure release for air tank (1/4").
  15. Plugs for excess ports in air tank (1/4").
  16. Two 48" lengths of 1" x 1/16" steel (approximate width/thickness).
  17. Various nuts, bolts and washers, including machine and sheet metal bolts.
  18. Electrical tape.
  19. Zip ties and duct tape - man's best friends.

The first task is removing the grille, which is as easy as grabbing it in a few key areas and giving it a sharp tug. Metal tabs secure the grille to the frame, making for easy removal and installation. This is good, because I removed and installed the grille approximately 132 times. Even the turn signal light bulbs are easy to remove - a quarter turn and they pop right out.

After the grille came off, an angular-shaped plastic piece, a trademark of these vehicles, was visible behind the license plate holder. I presume it is some sort of splash/debris guard to keep the radiator somewhat clean, but I had to pull it out to have any hope of mounting 4 horns behind the grille. After carefully prying out some plastic rivets and struggling with it like a Chinese puzzle box, I gave up and cut up the plastic into pieces.





Removing the grille part 1



Just 10 metal tabs....



Removing the grille part 2



...and two light bulbs. That's it.



Removing the grille part 3



It was remarkably simple, once I figured it out.



Grille be gone



With the grille removed, I found an oddly shaped plastic piece behind the bumper. This would have to go, or the horns wouldn't fit.



Plastic frustration



I tried to remove the plastic in one piece, but after quite some time Mr. Air Cutoff Tool paid a visit.



Plastic removed



This was much better.



Finally the grille is gone, and we're ready to get started.



Development



What I was left with was the hood latch frame in the center and a metal line that I believe goes to the power steering pump. The horns must be mounted around these obstacles, which is perfectly doable as long they're positioned in locations that also avoid the grille. We'll see later on, there's a small amount of metal which must be shaved off the right side of the hood latch frame. I also had to modify the air intake on each horn to get another 1/2" of clearance between the radiator and the grille.


Let's Start Building!

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