Only one horn works at a time

[Anthony]

I know it makes no sense, that's why it's stumping us. We didn't measure the voltage when the horns were connected, only when disconnected. But when they are disconnected, both sides give a 12V reading. Does this make a difference?

[JTGS850GL]

I know it makes no sense, that's why it's stumping us. We didn't measure the voltage when the horns were connected, only when disconnected. But when they are disconnected, both sides give a 12V reading. Does this make a difference?

Yes, this makes sense now. With no horn connected you have no current flow. The open wires would show full voltage and any high resistance connectors inline would not have voltage drops. Once the horns are attached, and current is flowing, the areas that have high resistance will start to drop the voltage across them and reduce the voltage going to the horns and reduce the overall current flowing through the system. You may be able to drive one horn because the voltage drop is not enough to stop it from working. Adding the second horn effectively doubles the current flow and creates a larger voltage drop across the high resistive connections. The result would be too little voltage getting to the horns and too little current to drive them.

Download a set of schematics and follow the horn wiring to locate where the voltage loss is. Here's a link to the schematics: http://members.dslextreme.com/users/...s-z_wiring.jpg

Start at the fuse box and locate the horn fuse that has an Orange Green wire. It passes through a connector and then to the horns. From the horns you have a Green wire that passes through a connector and then to the horn button and back through the connector to ground. Verify that your ground connections are in good condition as well. My guess is that either the fuse holder, one of the inline connectors or the horn button it self are dirty/corroded and adding resistance to the circuit path.

[Anthony]

That actually sounds very plausible. I will definitely check all this tonight. I have cleaned a lot of the inline connectors in general with electric cleaner, including inside the left hand control switch. Is it possible that the fuses are old and need replaced? Or just need to be sprayed with electric cleaner? I also don't want to screw up the fuse box...

[JTGS850GL]

Cleaning with contact cleaner may not be enough to remove corrosion. Sometimes it takes a fair amount of mechanical scrubbing to get the corrosion off. A dip in CLR (Calcium, Lime and Rust remover) will clean off the contacts pretty well, but remember to rinse and dry the contacts afterwards. Not likely that the fuse it self is bad, but the contacts that hold the fuse in the holder can get dirty. The actual horn button can get dirty as well.

[Anthony]

We still couldn't find anything. Resistance was good and the horns were both getting 12V even when connected. The only odd thing was when one horn was connected and we were testing the other side with the volt meter, when the button is pressed, it was pumping out about 19V to the terminal connectors on the non-horn side. Interesting...

[hjfisk]

19 volts!!! have you checked your battery, and regulator? Or maybe better yet your meter?

[Anthony]

The battery is brand new, and I haven't gotten to check the Rectifier or Stator yet. I was going to run a quick test after I get it inspected today. Everything else works great on the bike though, and one horn is no biggie for me. But of course it would be nice if I could get it to work.

[mrbill5491]

Add a horn relay, see what happens, When I went to a better horn for my bike, it worked fine until I got everything else wired back in, lights, coils etc. Horn no work, add relay now I have a 150db Blaster horn. I used the high pitch. Dang stock horn NEVER even came close to working like this one does.

[Anthony]

Where could I get another horn relay from?

[JTGS850GL]

Are you reading 19V with the engine off or on? Don't buy the 19V if the engine is off.

[Anthony]

It was 19V with the engine off. But even if the bike is on, both horns still don't work at the same time.

[hjfisk]

You really need to check your meter. I don't buy the 19 volts in the battery

[JTGS850GL]

No way you have 19V with the engine not running. My guess is that you're not using the meter correctly. First you say 12V now you say 19V.

[Anthony]

It was reading 12V when we no horns were connected at all. Then we put one on and checked the other terminal that was not connected, and while holding the button, it said between 18-19V. So maybe it is the meter, or we are taking it incorrectly. If so, what's the proper way to do it? Also, I did the quick check test (6 steps) that a member here posted to get a baseline reading of the electrical system, and all the reading were exactly to that post's readings. Only difference was when we revved the engine to 2500 and 5000, the volt read about .2 or .3 under the specified range, but that may have been because it was tricky to get the RPM's to hover in that range, because I had to adjust a lot. With that in mind, what should I do?

[Steve]

There is a lot of talk here about checking voltage, and you keep responding that it is 12 volts "even when both horns are connected". My question is "what is the voltage when you push the horn button and get whatever sound that you do get?"

You keep saying that it's a constant 12 volts, but you also said that the headlight dimmed when you pushed the horn button. There is no way the headlight will dim if the voltage is a "constant" 12 volts.

My guess is that the voltage is simply dipping because the battery can not supply enough current to feed both horns when the engine is not running. Is it any better with the engine running? You have reported that all the charging system tests seem to be good, so the horns should also be getting enough power.

If you don't want to run the bike every time you want to test the horns, you can also use jumper cables that are connected to the battery in a NON-RUNNING car. It will still only be 12 volts, not the 14 of a running bike, but the larger car battery will be able to supply enough current to keep the voltage from dipping very far below that.

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