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More importantly, how long do you expect to draw current, ie how long will you have the horn button depressed? Even if the current draw is close to the rated ampacity of the wiring, overheating will only occur if the current is drawn continuously for some period of time...short beeps, esp. intermittent beeps, will dramatically decrease the total power consumption.

Not exactly... running a device for a longer period will of course increase it's -total- current draw, but when any electric/electronic device is switched on it's current draw is greatest at the first moment of operation. That's why you get a small spark on the switch, and it's that very spark that'll weld the switch contacts together if you overload it.

Rather than "do I need a relay with this horn?" the question should be "Is there any reason NOT to use a relay with this horn?". Sure it may not NEED it... for that matter you don't NEED fuses either! Till something goes wrong the bike'll work fine without either, but for the sake of a $2 investment and installing one extra wire to the battery I'll take the relay any day.




'fraid not, Matt...running any device for a period of time won't change it's total current draw...time will determine the total energy used. If a circuit is designed to draw 5A of current, it will draw 5A of current until it's turned off, or until something goes wrong, ie shorted/open load or similar. Same with power...if this same 5 amps is delivered to a 100 ohm load, power dissipation will be 1000 Watts, and will be continuous. However, total energy consumed will be a function of power over time ie watts/hour.

A capacitive load will initially draw more current at turn on, an inductive load will draw less. Since a resistor is a phase linear device, current and voltage are both instantaneous...however, there are certain exceptions, and these are generally temperature and material based, ie a light bulb filaments resistance will dramatically increase with temperature (all metals have a positive temp. coefficient, that is dR/dt > 0) or so-called inrush current...and this is because the filament is tungsten, a metal.

Contact arcing generally occurs only with inductive loads, esp AC inductive loads, or with very high current DC applications.

My point in all this is that, as FJ said, this isn't a starter motor application, it's a horn! And a horn is used intermittently, unlike, say, high intensity driving lamps or something. I personally wouldn't spend any time worrying about installing a relay, or exceeding the ampacity of the wiring, etc. It's just a horn.

'02 Blk/Slvr BA, Jireh fishtails, Freak, no AI, 160/42, 18T She is the Beauty, I am the Beast.