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Thread: how many amps does a car horn draw

  1. #1
    airsmith282 Guest

    Default how many amps does a car horn draw

    the reason i ask is cause the book i have for the truck dont tell me nothing and 2 there is more then just the horn on the fuse.

    i need t bypass my steering wheel horn cause the click spring is shot and iam not spending 100 buck on a new one , i also dont want the citre version horn button its big and ugly , so i want a nice cool momentary button switch problem is the onesi can get are 3 amp AC 125 volt i need to accees only 12 volts DC so need to know if this switch will hadel the draw from the horn, i should also mention that i have 2 horns side by side on the truck there just normal car horns but there is 2 of them,

    thanks in advance for any help on this one

  2. #2
    Join Date
    Jan 2009
    Location
    Southern WI
    Posts
    161

    Default

    Run a relay like this: http://www.summitracing.com/parts/HLA-H41510121 and you will have NOOOO Problems.

    Regards,
    Keith

  3. #3
    Join Date
    Dec 2006
    Location
    Westminster, MD
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    204

    Default

    Do you have a meter? Just check them and then you will know the answer for sure.

  4. #4
    Join Date
    Jan 2003
    Posts
    177

    Default Horn

    airsmith282,
    Look to see if your vehicle has a horn relay, if so then the current draw of the horn will do you no good.

    If you have a horn relay the draw on the relay would be less than 5 amps @ 12 volts.

    Thanks,
    Paul

  5. #5
    Join Date
    Jul 2005
    Location
    Burnet, TX
    Posts
    2,128

    Default Another source

    You could buy the relays cheaper a surpluscenter.com. I have not bought any from them lately.
    Byron Boucher
    Burnet, TX

  6. #6
    Join Date
    Dec 2004
    Posts
    656

    Default

    get a 40A relay from summit: http://www.summitracing.com/parts/PCO-5591PT/

    if you go to an electrical/electronics supply house like newark, you can get a comparable relay for probably half that price: http://www.newark.com/jsp/search/pro...og&sku=21M4719 but you won't get the prewired base. you can use regular crimp on 1/4" female quick disconnects to connect wires to the terminals, though.

    40A is way overkill for a horn, but you'll be more than covered.

    you can most likely get away with just using the pushbutton. what's the make of your truck? i doubt whoever made it would use a heavy duty switch for the horn button on the steering wheel in the first place. there's probably already a relay somewhere in the circuit
    Last edited by psomero; 10-15-2009 at 11:07 PM.
    -paul

  7. #7
    Join Date
    Aug 2008
    Location
    Missouri, USA
    Posts
    1,353

    Default

    Year, make & model???

  8. #8
    Join Date
    Oct 2005
    Location
    British Columbia
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    3,694

    Default

    Airsmith like the others have said, get a relay.
    Go to your local Princess Auto,( gee I sure like that name ) and get a 30 amp 12 volt relay, $4.95 I think, and put it into the circuit.
    The relay acts as a transfer switch of sorts between the switch you are going to use and the load, i.e. headlights, horn, or whatever heavy load you are trying to turn on and off. Kind of like a starter relay takes the load off of you key switch. You can imagine the size of key you would need to activate the starter without a relay right?

    Horns can easily use 20 amps or more and to use a switch that is robust enough to handle that amount of current would require a large set of contacts. In order to use a more convenient size of switch a relay is used to do the bull-work of the switching work, in other words it carries all of the heavy current instead of your horn switch.

    I've included a simple wiring diagram to help with the installation.



    The numbers will be the same on the relay you purchase as it is a Bosch type relay, so all you need to do is connect a ground to #86, a fused 12V positive to #30, a 12V switched source (like your horn switch) to #85, and finally your horn to terminal #87.

    The relay has a small coil inside which closes a set of contacts inside to carry the main load that you want to energize. The horn button only has to carry a load of about 150 milliamps instead of 20 amps.

  9. #9
    Join Date
    Oct 2005
    Location
    British Columbia
    Posts
    3,694

    Default

    Like Psomero said, you vehicle probably has a relay, so if you can id it use it in the same manner as my previous post.

  10. #10
    Join Date
    Jan 2003
    Location
    Chilliwack, B.C.
    Posts
    9,462

    Default

    Willy has it right. Horns usually draw lots of current- 20 amps is not out of line. Where I once worked, an installer was told to put the horn honk relay in the trunk. He wondered about that, and asked me. I told him that there would be too much loss in the wiring and the horn may not work. He took that to 'management', who told him to not listen to me, just do it like he was told.

    It didn't work, so that became an issue with me to blame. Huh? I was once asked to attend a seminar with this manager, and in response I had to say ' well, I'll have to take a course in stupidity before I could do that'- got laughs from the rest of the staff, but not the management-

    At any rate, you do need a relay and you should keep the high current wiring as short as practical, and don't skimp on the gauge.

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