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Author Topic: '77 CB750K Horn Wiring  (Read 1737 times)

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Offline skamania19

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'77 CB750K Horn Wiring
« on: August 28, 2005, 04:16:49 PM »
I just got a 77 CB750 with the horn disconnected. I hooked up the black and green wires and turned on the key. Found out why it was disconnected, the horn came on. Checked wiring diagram and see horn should have black hot wire coming in and hot green wire coming out, to the horn button where it grounds when pressed. Is this correct? If that is true, how do I hook up the horn without it grounding through the bolt connection to the frame?  ??? The horn and all its mounting parts are metal. When I disconnect the horn from the frame I can't get it to work at all. Where does the horn button ground to?
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Offline Paul

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Re: '77 CB750K Horn Wiring
« Reply #1 on: August 29, 2005, 02:03:42 AM »
As far as I know ....without the diagram.
The horn has two terminals (Both of these are/ should be isolated from anything.) One ..Black goes to the Hot ignition circuit, and the green goes to the horn button where it is only grounded when the button is pressed. If your horn is always on, Your button may be bust (grounded all the time) or wait here for more...........
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Offline oldbiker

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Re: '77 CB750K Horn Wiring
« Reply #2 on: August 29, 2005, 02:10:24 AM »
You are right. The black wire is hot (live) when the ignition is switched on and goes to one side of the horn. The greenwire runs to the horn button and is grounded when the button is pressed. If the horn sounds without pressing the button, this suggests that the button itself is faulty. disconnect the green wire at the button and if the horn stops this confirms the button is faulty. It may be that the spring in the button has got misplaced or the contacts bent but it is possible to strip it out and examine it. If the horn still sounds when you disconnect the green wire at the button, then some where along its run the wire is shorting to ground and you will have to go along the run looking for the damaged point.
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Offline skamania19

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Re: '77 CB750K Horn Wiring
« Reply #3 on: August 29, 2005, 06:43:36 AM »
The horn only sounds when it is secured to the frame on its mount. This tells me that is where the ground is coming from. The green wire does not need to be hooked up so for now the green wire short theory doesn't seem to fit. It may be the wrong horn for the bike? It's all metal, round, with a mounting bolt in the middle. Seems to me that style of horn HAS to ground itself when mounted unless it's supposed to be mounted onto something plastic. Gotta be the wrong horn or the wrong mount, no?
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Offline Paul

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Re: '77 CB750K Horn Wiring
« Reply #4 on: August 29, 2005, 09:08:53 AM »
These Honda's only switch on the ground wire.
Typically horns with two terminals either switch ground or hot. If yours was meant to be grounded to the frame, then why are there two terminals on it?.
Throw it away.
Connect a meter to the green wire and the frame, you should only get continunity when the button is pressed, and your black wire should be live all the time with the ignition on.
Most horns are marked with + & -, if your wiring check is OK, buy a new horn they are cheap, If not go find where you threw it.
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Paul.
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Offline skamania19

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Re: '77 CB750K Horn Wiring
« Reply #5 on: August 29, 2005, 05:14:16 PM »
I like that idea. The horn was probably messed up and that's why it was disconnected in the first place. So now it's my newest discus. New horn sounds much simpler. Plus, throwing it makes me feel so much better! Thanks for the help.
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eldar

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Re: '77 CB750K Horn Wiring
« Reply #6 on: August 29, 2005, 05:41:41 PM »
Hell with the new horn! Just get yourself a air blast can with a horn on it! That way you can aim it at some dummy in a car so they know you mean them!!
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Offline Dennis

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Re: '77 CB750K Horn Wiring
« Reply #7 on: August 29, 2005, 05:57:49 PM »
Quote from: eldar on August 29, 2005, 05:41:41 PM
Hell with the new horn! Just get yourself a air blast can with a horn on it! That way you can aim it at some dummy in a car so they know you mean them!!

Why didn't I think of that myself. I have one of those downstairs. I think it came from a bicycle and even has a handlebar mounting bracket with it.
I like that idea.
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eldar

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Re: '77 CB750K Horn Wiring
« Reply #8 on: August 29, 2005, 06:12:07 PM »
Yeah just use those cans of air like you hear at football games! That would get attention FAST.
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Offline Paul

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Re: '77 CB750K Horn Wiring
« Reply #9 on: August 30, 2005, 12:11:08 AM »
And the faster you squeeze the rubber ball on the end...the louder it gets  :D
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Offline BobbyR

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Re: '77 CB750K Horn Wiring
« Reply #10 on: August 30, 2005, 04:41:07 PM »
You may want to look at the horn button itself. Inside it is simple spring and contact. There is a wire in there with a thick pice if shrink tubing on it. In my case it was out of place and caused the horn not to work. In your case it may be doing the opposite. Of course mine went bad the day before my State inspection. So I went to WalMart and got the cheapest bike horn which was a pink Barbie tyoe think. Not only did I pass inspection, but a guy at a stoplight blew me a kiss.
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Offline skamania19

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Re: '77 CB750K Horn Wiring (UPDATE)
« Reply #11 on: September 02, 2005, 09:12:10 AM »
I tossed the old horn. Felt pretty good too! Got a new one on board that is the right one. I found that with this new horn I have power going all the way to the button. If I ground that wire the horn actually works. HOWEVER, the button apparently is not grounding the wire when depressed. Does anyone know where the button actually goes to ground? Is it a wire leading to the frame? Would that be the wire BobbyR spoke of? Or does it ground through contact with the handlebars? The wiring diagram I have just shows that it grounds, but doesn't say where or how it does it. If I can find the ground I can find out if the button is bad or if it just isn't grounded. I'll tear it apart tonight, perhaps the answer will be self evident.
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Offline skamania19

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Re: '77 CB750K Horn Wiring
« Reply #12 on: September 02, 2005, 06:48:16 PM »
Well, I tore it aprt and learned the horn was grounded through the handlebar and the horn button was tatered. Replaced it with a parts button and it works!  ;D
Thanks everyone for your input.
skamania19
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