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Only one horn works at a time

  • Thread starter Thread starter Anthony
  • Start date Start date
A

Anthony

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Hey all,
I'm brand new here, so it's great to be a part of this community. My first question for you all is stumping me and my dad. We have been working on my 1982 GS750E that we picked up Thursday, and have been fixing various issues with it with success. But the issue with the horn is annoying, because only one horn works at a time. I replaced both horns with new ones from an auto parts store, and updated the connectors that were on the old wires. Both sides are getting 12V, according to our volt meter, so there shouldn't be a short. When you disconnect one side, the other side works, and vice versa. So for the time being, I have only one connected and centered it on the bike. We also checked the splice, which looks good. Any suggestions? Thanks!
 
Maybe the new horns have a different impedance than the old? Did the stock horns have the same issue?
 
Have you ran a jumper from one to the other and only used one of the harness connectioins for power?? Run them in series off one set of plugs???
 
The old horns did the exact same thing, so I know the new horns aren't the problem. And how would I run a jumper between them?
 
Just run a wire from one horns 2 terminal to the other horns two terminals...then see if both work when you hit the button. Dad will know what a series is and can help you.
 
I'll definitely keep that in mind. Also, we noticed that the headlight seemed to dim a lot more when both horns were hooked up, and they made a weird clicking noise, like it was trying to sound but couldn't buzz. The weirdest thing, that's for sure. How come a series might work? I'm interested in the reasoning behind it.
 
Was thinking that if one set of wires was bad...then....but then youve added yet more details. So I am not sure a series will do squat..but you can try.
 
Well both sets of wires are showing 12V when the button is pressed, and we even checked the switch to see if something was loose or broken, but the switch is fine too.
 
Exactly. And actually, the higher tone horn did have a tendency to not always sound, but the lower tone one is very responsive. I also tested both of the old stock horns, and neither of them would work in conjunction with the new horns.
 
Look at the backs and see if theres a small phillips head with a jam nut. Loosen the jam nut and ever so slightly turn the screw. this is an adjustment for the pitch. Maybe its just not adjusted right from the factory..it happens.
 
I just tried adjusting the pitch on both the new old horn, but still no luck with both. But now when both are connected, only the left one works, which is the new low tone. Does that help any?
 
What is the voltage to the horns while you are pushing the button? sounds like a dirty connection somewhere and you have voltage drop when the button is pushed. My guess is it is in the button itself
 
The voltage was reading 12V on both sides when the button is pushed, so there is no voltage drop.
 
This makes no sense if you're getting a full 12V across the horns when the button is being pressed unless the automotive horns need more like 13.6V to work properly. I just need total clarification on this... With both horns connected, and the button pressed, you measure 12V across the two horn terminals on each horn with no sound.
 
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?
 
Anthony said:
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?
Click to expand...

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/storagecliff/images/750e-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.
 
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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...
 
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.
 
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...
 
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