Horn wiring question

My 72 Norton is fitted with a CNW electrical master switch. My horn does not work - I swore it once worked. I checked the horn and it works when I apply 12v fom the negative side of the battery so no issues with the horn. I am not seeing any power at the purple and black wire. The red ground wire has continuity to the frame. According to the CNW documents I have, I should see hot power at the red wire that comes out of the master switch but I am seeing nothing. I have continuity from the green/purple wire that connects to the horn to the Green/purple wire at the switch. Any thoughts on what I have wrong or how I can trouble shoot this? I have a sort of dyslexia for wiring.

Yorkie said:

I am not seeing any power at the purple and black wire.

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The fault could then be the handlebar switch.

Yorkie said:

The red ground wire has continuity to the frame.

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The red ground wire shouldn't need continuity with the frame as the red wire is ground not the frame.

Yorkie said:

According to the CNW documents I have, I should see hot power at the red wire that comes out of the master switch but I am seeing nothing.

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I don't understand that. Is the electrical system negative ground or what is that red wire connected to, otherwise it should not be hot?

Yorkie said:

I have continuity from the green/purple wire that connects to the horn to the Green/purple wire at the switch.

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You said purple/black (sorry my mistake you did say purple/black) so is that what you mean, not green/purple or can you explain green/purple as there's no green/purple in the standard harness except for a short length of the Interpol wiring?

Thank you for the reply. The bike is positive ground. I am using an aftermarket CNW Master Switch connected to a new standard loom. On my bike, the red wires are the ground wires , which are also connected to the frame of the motorcycle at the top motor mount. The CMW Master Switch has a green / purple wire coming out of the switch and that is connected to the purple black wire that connects to the horn. According to the CNW paperwork (attached) the red wire from the master switch should have 12V of power - but mine does not. Everything else works (turn signals : headlight hi/lo) just not the horn.

Yorkie said:

The CMW Master Switch has a green / purple wire coming out of the switch and that is connected to the purple black wire that connects to the horn.

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Horn purple/black is normally powered by white that goes to the handelbar cluster not a red from the ignition switch. In that case where is the horn switch?

Except for brown the other wires from the CNW switch also make no sense to me.

Send Matt an email.
He usually very good at helping out.

The horn switch is an aftermarket one supplied by Colorado Norton Works. The master switch contains the headlight (hi:lo) , turn signals and also the horn button. I assumed that there was a common 12v feed going into the master switch with power coming out. My white wires are hot with 12V with the ignition turned on.

Yes, this CNW "master switch" is in fact a handlebar switch cluster so now it is making more sense.

What's normally referred to as the master switch is the ignition switch.

As far as troubleshooting.
You have power to the switch as you have lights.
On your multimeter, Clip the red to ground.
Then check each lead out of the switch for power as you push the horn button.
That's your hot horn lead. Tie it into the purple and black and toot away.

As green/purple apparently connects to purple/black then red seems like power in to the switch so what does red connect to, hopefully not harness red as that wouldn't work?

RED "12v power (hot) for horn."

Yorkie said:

Thank you for the reply. The bike is positive ground. I am using an aftermarket CNW Master Switch connected to a new standard loom. On my bike, the red wires are the ground wires , which are also connected to the frame of the motorcycle at the top motor mount. The CMW Master Switch has a green / purple wire coming out of the switch and that is connected to the purple black wire that connects to the horn. According to the CNW paperwork (attached) the red wire from the master switch should have 12V of power - but mine does not. Everything else works (turn signals : headlight hi/lo) just not the horn.

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The cNw switch red wire needs to connect to a harness white wire. In the standard positive ground harness, white is hot whenever the bike it turned on. If you have the cNw switch red to a harness red then you have the switch red grounded.