Question about wiring for train horn.

Maheriano · 09-17-2009, 01:24 PM

This is completely unrelated to computers, I just figure people here would know a lot about wiring and voltage/amperage.

I wired up a train horn in my car last night, it's a simple wiring job with power going from the battery to a 12 volt relay, then to a small compressor which sends air out to the horns. I wish I had the relay in front of me to list the numbers but it goes something like so:

- horizontal 87 pin to the + on the compressor
- another pin to + on battery
- another pin to - on battery
- another pin to push button inside car.
- other end of push button out to + on battery
- negative pin on compressor to - on battery

Everything works meaning it's hooked up correctly, it all works fine. I'm just wondering about the wiring, I used 18 gauge wire for this and I'm thinking now that it's carrying a 12 volt current so that might heat up the wire to a point of melting, do you think? Or does it only pull the full 12 volts when you push the button and send the power through the relay? It's all 18 gauge wire for the whole install so will it heat up the wire on its own or only if the button is held down for an extended period of time? Should I be worried? Should I replace the wire at certain spots? All wires are shorter than about 2 feet except the push button wire......it's about 7 feet.

GizmoQ · 09-17-2009, 11:03 PM

I've got Siege Train Horns on my car.

8 trumpets, 5/8" air lines, 8 gal tank, 200PSI, 148dB.

I don't know which system/compressor you have, but I would recommend changing the power wires from the battery to the relay and the relay to the compressor to at least 8 guage. I went for overkill and mine's 4 guage. The reason I say this is I have already burned out one compressor cause it wasn't getting the Amps nor Voltage it needed. I had a Viair 350C (235Watts) and have since upgraded to a Viair 480C and its 260Watts. Bottom line its not gonna be happy if the battery voltage drops below 13V.

After realizing this, I also put in a kill switch to a relay on the compressor power line so I can completely shut it down if I need to. I have also upgraded my alternator and done a BIG THREE wiring upgrade. I never let my compressor run when the engine is not running and I clean my tank once a month at least.

Tell me more about what horns, what compressor, and your air supply lines you have and I should be better able to assist you.

hondaboomer · 09-19-2009, 02:03 AM

im new here and i like it i poot a pare of mac truck hors on my honda what i did very simpel i have a old diving tanck taped the lines in ran air hoses to the 12dc air solinoid and taped in a 3 way swich from home depot and splysed it in betwean my normal horns so when i whont my air hors i just flip a swich and use my hore butons on my stering wheel

Maheriano · 09-19-2009, 08:50 PM

Well that was a friend's car I wired up on the 18 gauge, I just put the same setup in my car with all 10 gauge wiring. I decided to use 10 and not 8 because it takes a 30 amp inline fuse the wiring on that fuse holder is 10 gauge so I figured I'd match it all the way around.

So I have another question, the button I'm using to activate the horns has a power wire going to the battery and then there's another going to the relay. The one with the relay has a 30 amp inline fuse as per the installation instructions but the button doesn't call for a fuse at all. Should I put one on it or just hook it directly to the battery?

GizmoQ · 09-20-2009, 12:05 AM

Quote: Originally Posted by Maheriano

Well that was a friend's car I wired up on the 18 gauge, I just put the same setup in my car with all 10 gauge wiring. I decided to use 10 and not 8 because it takes a 30 amp inline fuse the wiring on that fuse holder is 10 gauge so I figured I'd match it all the way around.

So I have another question, the button I'm using to activate the horns has a power wire going to the battery and then there's another going to the relay. The one with the relay has a 30 amp inline fuse as per the installation instructions but the button doesn't call for a fuse at all. Should I put one on it or just hook it directly to the battery?

You still haven't told me about your setup so it's hard to say. My instructions were similar and I thought "idiotic!" I changed mine to positive from battery to 30A fuse to horn relay and the ground side coming into the cockpit for the switch. OBTW, I mentioned earlier that I burned out a previous compressor with low voltage, well guess what - that 30 Amp fuse holder you mentioned, melted beyond recognition without blowing, I was lucky (I now keep a fire extinguisher in the trunk).

So tell me more about the brand, specs, and layout. For instance, my switches (yes more than one) are at the horn vice on the tank which means I have a 21 Ft supply line fully pressurized all the time. I did this because I wanted full pressure immediately when switched on as opposed to waiting for the pressure to build and flow that distance - it just sounded weak to me as the pressure built up.

hondaboomer · 09-21-2009, 01:37 AM

well my set up would probely be considered hoj poj butt i have a air tank but no conpreser and the only thing my swich is powering is a ais soliod but i had a air horn on my s10 from pepboys and i just strate wierd it and never had a problem no fusibel links

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