What is a relay (as in an automotive "horn relay")?

I had just put in an air horn into my car last night and the cars 10amp fuse blew (in the cars fusebox)! I called the air horn manufactuter and they said I needed a "relay". Asked by technoreid69 62 months ago Similar Questions: relay automotive horn Recent Questions About: relay automotive horn Education & Reference.

Similar Questions: relay automotive horn Recent Questions About: relay automotive horn.

A relay is a switch A relay is an electrical switch that can be opened or closed by an electrical signal. It is an electrically controlled switch, in other words. People use them when they want a small amount of electricity to control a bigger amount of electricity.

The same thing can be done with transistors, but transistors can't handle the amount of current that relays can. So what probably happened with you was the air horn pulled more current than your fuse could handle. You could replace the fuse with one with a higher rating.

What they are suggesting seems to be to use the usual car horn circuit to control a relay which then gives power to the air horn. That way the car horn circuit doesn't see the current being drawn by the air horn. It would also mean the air horn is not protected by a fuse.

But perhaps one is built into the horn, I don't know. Hope this helps! .

10A fuse protects horn switch (in steering wheel) & wiring. Horn relay allows larger Amp horn. 10A fuse protects horn switch (in steering wheel) & wiring.

Your need your air horn connected to a larger amp fuse (based on air horns amperage rating). Horn relay allows you to use existing horn fuse, switch, and wiring with larger Amp air horn. A horn relay is a larger Amp-rated switch, which is actuated by a smaller amp electro-magnet,which is controlled by your existing horn switch in your steering column.

Alternative would be to rip you steering wheel apart and put in a larger Amp-rated switch and wiring and replace the 10A fuse. Adding a horn relay is usually much simpler. Horn relays (one vendor of many):tessco.com/products/displayProducts.do?g... search for "Horn relay":http://www.google.com/search?hl=en&q=%2B%22horn+relay%22&btnG=Google+Search Sources: http://www.tessco.com/products/displayProducts.do?groupId=619&subgroupId=63 .

Relay is a swich that will protect your circuit. Depends on how you are installing the air horn, you might not need a relay. You can consider relay as a swich that will open/close a ciruit based on the input from another circuit.

I’ve seem two ways people installing the horns, they either remove the stock horn and wired up the air horn to the stock wire OR you are keeping both horns and wired the air horn in parallel to the stock one? For thos who have removed the stock horn the just simply replaced the fuse to a higher rated one since the air horn will draw more power. (for example, plug in a 15mAh instead of replacing the blown 10mAh) You’ll need to look at the air horn you have and figure out how much current it draws.

15mAh should be enough for most of the smaller ones but I’ve seem as much as a 30mAh fuse was needed for more powerful horns. The most popular way of install is illustrated as below. Above is a sample relay wiring for a Hella’s air horn.

As you can see the relay (the unit on the top) has 4 pins and they are wired to the ground, + from the battery, the compressor and the stock horn replay. The stock horn doesn’t require much power so if you simply wire the air horn to the stock harness, you will either not get nearly as loud or risking burning up the stock horn relay/switch due to the higher current draw. The relay in the picture will make sure the air horn gets all the power from the battery directly.

Basically the horn button on your steering wheel will act as a trigger, whenever it gets pressed, the replay will close the cuirt and gets power from battery directly. Whenever a relay is used, it is suggested to put another fuse in between the relay and + terminal on battery. Also, make sure you use the right wires (proper gauge) for the horn so the they won’t get too hot (wires too thin) or get current drop (wires too thick).

Most often a 18 Ga wire should be good. You can get a bosche 4 point replay in radio shack for around 4 bucks. NOTE: there are different power ratings for the relays, 15amp 30 amp, etc. Pick one based on your horn's rating/requirement.

(Hella air horn kit comes with a 30amp relay and most of the time 30amp is good for most application unless you got one huge horn. ) silvscorp's Recommendations 12VDC AUTOMOTIVE RELAY SPDT 30A .

It's a type of switch that allows one electrical circuit to control another. Automotive-style miniature relay (Image and caption from Wikipedia) Typical configurations are "normally open" and "normally closed. " There are a wide variety of other configurations and options within and beyond those two broad categories.

The way it works is really pretty simple. In the most basic form of the switch, low power circuit is attached to an electromagnet that operates a mechanical switch. This switch opens or closes a circuit carrying much higher power.

The electromagnet can pull the switch open (for normally-closed relays), or pull it shut (for normally open relays). So in the example you cite, a low-power circuit running to the steering wheel is activated when you press the horn button. The horn relay’s electromagnet is activated by the small current from that circuit, which pulls the relay shut, closing the horn circuit and allowing current to flow to the horn.

Releasing the horn button opens the low-power circuit, cutting power to the relay. The relay drops open, and the horn, now unpowered, shuts off. Lots of other stuff in cars relies on relays of one sort or another, like the turn signals.

If you’re curious, the relay was invented by Joseph Henry. Sources: Too much time under the hood of my car. Wikipedia.

Joram's Recommendations Electronics For Dummies Amazon List Price: $21.99 Used from: $11.64 Average Customer Rating: 4.0 out of 5 (based on 23 reviews) Google Map Joseph Henry was born in Albany. View Larger Map Video .

An electrical switch Relay From Wikipedia, the free encyclopedia Jump to: navigation, search This article is about the electronic component. For other uses, see Relay (disambiguation). Automotive style miniature relay A relay is an electrical switch that opens and closes under control of another electrical circuit.

In the original form, the switch is operated by an electromagnet to open or close one or many sets of contacts. It was invented by Joseph Henry in 1835. Because a relay is able to control an output circuit of higher power than the input circuit, it can be considered, in a broad sense, to be a form of an electrical amplifier.

Sources: http://en.wikipedia.org/wiki/Relay .

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