I have a 2001 Fatboy FLSTI.
The horn wont work and it's kicking my butt. Here is what I have done. If I leave the ground on the horn and apply 12v straight from the battery to the other side of the horn it works. (Proven good ground, right?)
When I push the horn button I measure 12v between the 2 wires (Positive and Ground) that attach to the horn. (Proven good switch right?)
When I connect the leads back to the horn I DO NOT get 12v reading any more. It reads 0V when I push the button. What the heck am I missing here? Is it possibly a bad horn anyway. Does the voltage drop to 0v because of some sort of relay that I'm missing. I'm at a loss. ALL the other lights work. Left and right turn signals. Low\High beam. Hazards, rear brake light. ignition On\Off and Stop\Run.

Thanks in advance for your help.

 

Sounds like the horn is either open or shorted internally (bad horn).
Rreplace or substitute another horn to verify.

 

Thanks for the reply. I bought a new horn tonight. Still doesn't work. I have the maint manual but I'm going to try to find the electrical manual # 99495-01

 

A voltmeter will read the voltage difference between the positive probe and the negative probe.

When you connect a voltmeter across an opening in the circuit (such as the disconnected wires from the horn) it sees 12 volts on one side (the wire going to the switch) and 0 volts at the ground side, so the meter will show 12 volts.

When you connect the voltmeter to the two wires when they are connected to the horn (and the horn button is pressed), there are 12 volts on both wires, because the circuit is complete. The voltmeter will read 0.

Make sure the connector terminals on the horn and the wires are in good condition, because it sounds like everything is working correctly...

 

Positive (switch) has not been tested for AMPS if i read this correctly.
A weak positive connection would carry volts but very little amps and when the horn button is pressed with horn installed you would read "0" , and get no noise.
Switch might be bad or dirty contacts.

 

I am in agreement with im, since you know the horn works when it gets 12volts, and the ground is good, it is probably the switch not making good enough contact to supply sufficent current to the horn, or a bad connection at one of the connector plugs.

 

Thanks Guys. "IM" I only tested the switch for volts. Not Amps. Do you know how many amps it should read? I am going to dig a little further tonight and see if I can short the wires up at the switch. Unfortunatly it is sealed so I'll have to dig into the wires to short them. Any good ideas on how to do that without too much damage to the wires?
Thanks again for everybodies help!

 

I got it guys. I took the switch housing apart and shorted the 2 wires with sewing needles. I stuck them into the the sheathing and shorted the needles. Horn worked so it was a bad switch. Like my Dad always said, "If it's broke, don't be afraid to take it apart. The only thing you can do is fix it. It's already broke." So I took the switch apart and forced the wires back into the sealed unit. Don't know how long it will last but at least I can pass the safety inspection now. Also if it happens again, I know right where to look. Thanks for everybodies help. I really appreciate it.