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Install guide

Where the horn goes, and how to feed it air. Use it with the 3D fit view.

These are general starting points, not a pressure rating for the T-Series and not a replacement for the instructions from your vehicle's maker and from the makers of your tank, valve, hose and fittings. No pressure rating has been established for the T-Series. Every part in your system must be rated for the pressure you run. Start well below it and work up slowly, with everyone clear.

The air system at a glance

Air system layoutCompressor feeds a check valve, then a tank with a relief valve, gauge and drain. A line runs to a quick-acting valve next to the horn inlet. A relay, fuse and button switch the valve.CompressorCheckvalveTankValveHornLine, no smaller than the valve portWithin 12 in (30 cm)of the horn inletPressure gaugeDrain valveRelief valveRelay, fuse and button
The order things go in. Amber is air. The dashed lines are the tank fittings and the wiring.

A compressor fills a tank. A quick-acting valve at the horn releases that stored air in a burst. Everything between the tank and the horn decides how fast and how full that burst is.

Starting sizes

These are common starting points for large air horns, by chime count. Check each part against the pressure you run.

T-SeriesValveLine, tank to valveTank
1 or 2 chime1/2 inch port3/8 to 1/2 inch3 gallons or more
3 chime1/2 inch port, Cv 5.5 or more1/2 inch inside diameter5 gallons or more
4 or 5 chime1/2 inch, Cv 5.5 or more; 3/4 inch only with a 3/4 inch line1/2 inch inside diameter at least (not 1/2 inch OD tube), 3/4 inch best5 gallons at least, 10 or more for long blasts

Airflow

  • Air is stored in the tank and released in a burst. The line and the fittings decide how full that burst is far more than the valve: a 3/4 inch valve on a 1/2 inch line gains almost nothing, and 1/2 inch OD DOT tube is only 3/8 inch inside.
  • Use full-bore fittings on the main line. No push-to-connect fittings, quick couplers, needle valves or reducing bushings: one necked fitting undoes the line you paid for.
  • Mount the valve as close to the horn inlet as you can, ideally within 12 inches (30 cm), and keep the line from valve to horn short and straight.
  • Put the tank near the valve. A long line between them wastes the burst you stored.
  • Fit a relief valve on the tank, set below the lowest pressure rating of any part in the system. Add a pressure gauge and a drain valve at the lowest point, and drain the tank regularly.
  • Use a pressure switch matched to your compressor, and a water trap or dryer if you drive in damp or cold places.
  • Wire the valve through a relay and a fuse, with the button on its own circuit.

The valve, and where it goes

  • Use a full-flow, quick-acting electric air valve. Graham-White is one maker of these, and the points below apply to that style of valve.
  • Mount the valve within about 12 inches (30 cm) of the horn's air inlet. Its job is to open fast right at the horn.
  • Follow the valve maker's instructions for which way up it mounts. A coil facing up is common, so water drains away from it.
  • Match the port sizes. The line into the valve and the line out of it should not be smaller than the valve port.
  • Do not tee anything else off the line between the valve and the horn.
  • Keep the coil and its plug out of direct spray, and use a sealed connector.
  • Mount the valve to the frame or a bracket, not to the horn, so vibration and the weight do not load the horn's inlet.

Where it goes on a vehicle

Semi tractor

Plenty of room and frame to bolt to. The rule is to face forward, stay away from heat, and use a separate air supply.

  • Behind the front bumper, on the frame. Clear line of sound straight ahead, solid steel to bolt to, and the shortest run to a tank under the cab.
  • Cab roof, ahead of the sleeper. Carries the sound the furthest, but it adds height and the air line is long.
  • Behind the sleeper, near the fifth wheel. The cab blocks the sound and a coupled trailer sits right there.

Never tee into the truck's brake air system. Use a separate tank and compressor, or the truck maker's approved accessory air port with a pressure protection valve.

Flatbed truck

The same idea as a semi: face forward on the frame. The deck and headache rack get in the way of anything behind the cab.

  • Behind the front bumper, on the frame. Open line of sound and a short run to a tank mounted under the cab.
  • Cab roof. Good sound, but the cab roof is short and needs reinforcing.
  • Under the deck, behind the cab. The cab blocks the sound, and the space is tight around the driveshaft and exhaust.

A flatbed with air brakes has the same rule as a semi: keep the horn on its own air supply unless the truck maker approves an accessory port.

Pickup, SUV or van

Space is tight, so the frame behind the front bumper is the one good place. Check what is behind it before you drill.

  • Behind the front bumper, on the frame. Open sound path and strong mounting points.
  • In the bed. The cab is in front of the bells and the sound bounces back at you.
  • Under the body, behind the front axle. Low clearance, exhaust heat and road debris, with the body in the way of the sound.

Any vehicle

  • Bells face forward and clear of people, with nothing in front of the mouths.
  • Mount to the frame or to structure, not to plastic trim, body panels or the bumper cover.
  • Tip the bells down 5 to 10 degrees so rain and condensation can drain out.
  • Keep at least 12 inches (30 cm) from the exhaust, turbo, brakes and anything hot. The horn is plastic and it softens around 70 C.
  • Keep the tank and valve close to the horn, with short straight lines.
  • Check local rules before you fit one. Many places restrict train style horns on public roads.

Not sure about your setup? Send me a message with your vehicle and what you have, and read the Safety notice.