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#1 |
Registered User
Join Date: Jul 2013
Location: New Bridgeville, Pa
Posts: 45
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Is the Horn Relay really needed?
Is the Horn Relay really needed? I see the term "horn relay" everywhere in automotive forums. I am completely rewiring my 51 3600 to 12 volt. I made my own eaier to see and understandable diagram from following the original wiring diagram and it shows no horn relay, nor did I find anything that resembles a horn relay when I cut out all the wiring. Do I need one?
So everyone can critique my wiring diagram, I attached it as a picture, but it is originally created on powerpoint.
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Mgeez Felton, Pa. My toys: 1951 Chevy Truck 3600, 1952 Chevy Truck 3800, 1954 Case 411B, 1939 Ford 9n, 1972 Kubota B7100 http://s1282.photobucket.com/user/m_geesey/library/ |
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#2 |
Registered User
Join Date: Oct 2005
Location: Overland Park, Ks.
Posts: 5,204
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Re: Is the Horn Relay really needed?
The AD trucks didn't use a relay, but if you are running 12 volts you should put one in the circuit. If you use a horn with only 1 term. You will have to use a relay.
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#3 |
Senior Member
![]() Join Date: Aug 2010
Location: Shasta Lake, CA.
Posts: 1,619
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Re: Is the Horn Relay really needed?
On the 6v system (2 wires on horn )the horn was grounded at the steering wheel when the horn button was pushed. Making a large spark that could be seen at night, a bit disconcerting to the driver and passenger. Since most of the trucks saw daytime use it wasn't much of an issue.
On the 12v system the horn (1 wire on the horn) is grounded at its mount. It used a relay that put 12v to the horn when the horn button was pushed and grounded the relay, plus no spark at the steering wheel. There are 2 wire 12v horns on the market that could be used without a relay but they sound like a foreign car.
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Glen & Jane's Rides ‘57 GMC NAPCO Long Bed V8 4 speed Bought 2008 7 other cars & trucks , 5 trailers '56 Chevy Long Bed I6, 4 speed Bought 1990 Sold 8.22.2020 ’56 GMC Suburban Pickup V8, 4 speed Hydramatic Bought 1996 Sold 10.11.2020 My Other Tinkerings http://67-72chevytrucks.com/vboard/s...75#post8967275 |
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#4 |
Registered User
Join Date: Jul 2007
Location: Toppenish, WA
Posts: 15,415
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Re: Is the Horn Relay really needed?
relays are used to cut the electrical load on the switch that in this case is the horn button along with allowing you to run a smaller size wire to the horn button.
As G&R's57GMC said above some older systems ran a hot wire to the horn button and a wire from the horn button to the horn. Now most electrical systems have a single wire running from the horn relay to the horn button which goes to ground, there is a hot wire that runs from a terminal that usually has power all the time to the relay and then the wire from the relay to the horn. When you hit the horn button you ground that side and it activates the relay which in turn sends power to the horn. That's a bit long and drawn out but on a horn system it usually always works that way. On other systems with relays you use the relay so that you can get full power to the item you are operating like a pair of high wattage halogen headlights but you don't have the high amp draw through the headlight switch and the dimmer switch or what ever switch you are using for the system you are running. Hope I haven't added to the confusion.
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Founding member of the too many projects, too little time and money club. My ongoing truck projects: 48 Chev 3100 that will run a 292 Six. 71 GMC 2500 that is getting a Cad 500 transplant. 77 C 30 dualie, 454, 4 speed with a 10 foot flatbed and hoist. It does the heavy work and hauls the projects around. |
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#5 |
Registered User
Join Date: Jun 2006
Location: Idaho
Posts: 8,800
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Re: Is the Horn Relay really needed?
RElays are your friend for any power hog device light lights, radiator fans, most ac components, etc. Read this (whole site has good info on wiring and other stuff) http://www.alanhorvath.com/54chevy/u...ing_relays.php
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1959 Chevy Short Fleetside w/ 74 4WD drive train (current project) OrrieG Build Thread 1964 Chevelle Malibu w/ 355-350TH (daily driver) Helpful AD and TF Manual Site Old Car Manual Project |
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#6 |
Registered User
Join Date: Jul 2013
Location: New Bridgeville, Pa
Posts: 45
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Re: Is the Horn Relay really needed?
Will my orig 6v horn work on 12v? If I understand this right, the only thing the relay will do is minimize the spark at the steering wheel button. If I use a relay, should I place it on the neg side of the horn to complete the ground when the button is pushed?
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Mgeez Felton, Pa. My toys: 1951 Chevy Truck 3600, 1952 Chevy Truck 3800, 1954 Case 411B, 1939 Ford 9n, 1972 Kubota B7100 http://s1282.photobucket.com/user/m_geesey/library/ |
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#7 |
Registered User
![]() Join Date: Apr 2010
Location: Warrensburg, MO
Posts: 2,690
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Re: Is the Horn Relay really needed?
OrrieG... x2 on relays are your friend. I relay all my hi-amperage accessories on every build!
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www.olesargecustoms.com email: chris@olesargecustoms.com '48 build: http://67-72chevytrucks.com/vboard/s...d.php?t=541904 '33 build: http://67-72chevytrucks.com/vboard/s...=1#post6232888 '49 build: http://67-72chevytrucks.com/vboard/s...=1#post6364475 |
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#8 | |
Registered User
Join Date: Jun 2012
Location: Southern Iowa
Posts: 944
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Re: Is the Horn Relay really needed?
Quote:
Last edited by Highsider; 08-30-2013 at 10:13 PM. |
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#9 |
Registered User
Join Date: Jul 2013
Location: New Bridgeville, Pa
Posts: 45
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Re: Is the Horn Relay really needed?
Thanks all for the advice. The alanhorvath site really helped me understand.I edited my wiring diagram to include a horn relay.
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Mgeez Felton, Pa. My toys: 1951 Chevy Truck 3600, 1952 Chevy Truck 3800, 1954 Case 411B, 1939 Ford 9n, 1972 Kubota B7100 http://s1282.photobucket.com/user/m_geesey/library/ |
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#10 | |
Senior Member
![]() Join Date: Aug 2010
Location: Shasta Lake, CA.
Posts: 1,619
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Re: Is the Horn Relay really needed?
Quote:
A relay acts as a remote controlled switch. Power Flow left to right Bat._Fuseable link__12v Source_14GA.______/ ________ Horn____________Ground Bat._Fuse_________12v Source_24GA.__relay Coil______Horn Button _____Ground The horn wire would be 14 gauge to carry the high current the horn needs The button wire would be 24 gauge, would be very low current for the relay coil.
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Glen & Jane's Rides ‘57 GMC NAPCO Long Bed V8 4 speed Bought 2008 7 other cars & trucks , 5 trailers '56 Chevy Long Bed I6, 4 speed Bought 1990 Sold 8.22.2020 ’56 GMC Suburban Pickup V8, 4 speed Hydramatic Bought 1996 Sold 10.11.2020 My Other Tinkerings http://67-72chevytrucks.com/vboard/s...75#post8967275 Last edited by G&R's57GMC; 08-30-2013 at 01:40 PM. |
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#11 |
Registered User
Join Date: Jan 2012
Location: Motown
Posts: 7,677
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Re: Is the Horn Relay really needed?
probably yes, in short bursts
it may sound like a little girl screaming though ![]()
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cool, an ogre smiley ![]() how to put your truck year and build thread into your signature shop air compressor timer |
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#12 |
Registered User
Join Date: Feb 2012
Location: Brigham City Utah
Posts: 157
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Re: Is the Horn Relay really needed?
I have used the original relays and horns on 12 volt conversions on a 50 truck and a 51 truck. The horn will sound different. You definitely want to continue using the relay.
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#13 |
Registered User
Join Date: Mar 2012
Location: Lakes Region NH
Posts: 3,171
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Re: Is the Horn Relay really needed?
Some of the old horns have a screw on the side which can be adjusted to alter tone. I've done this after putting a 12V horn a 24V system.
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