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Horn hook up advice

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Whitephrog

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The good new is that my restored original BE horn works very well. The bad news is that my restored original BE horn works very well all the time. If I hook up the two battery terminals the horn blows. I'm using a Lacarra steering wheel with a Moto Lita boss. I thought that might be the problem in that the horn switch might be making constant contact. Removed the horn push and the switch. Horn still honks when the battery terminals are hooked up. Will it help if I reverse the two wires to the horn? I guess the answer to that is try it and see. What else could I have done wrong?
 
Did you restore the horns?

Could be that a wire is grounding inside the horn.
 
The following is "generic" information relative to Lucas horn wiring on BMC cars.

Until the mid-1960s, there was no horn relay. The horn(s) had two terminals. One terminal received a "purple" wire that was always electrically hot. The other horn terminal has a "purple/black" wire that goes off to some form of slip ring in the steering column. The slip ring type varies between makes and models. The slip ring provides a connection to one side of the horn button with the other side of the horn button providing a path to ground. When you push the horn, you are making a ground connection.

To test for a ground short in the horn as Trevor suggests you should be able to disconnect both wires from the horn and then selectively connect the purple wire to one horn terminal, then the other. If the horn sounds, you have an internal short in the horn. If not, leave the purple wire connected to one of the horn terminals and connect the purple/black wire to the other. If the horn sounds, you have a short to ground in the purple/black wire or a wiring error in the horn button itself.
 
X2 on the above.
Note, that the Sprite/Midget horns are different than most, in that they have two connections, both isolated from ground.
If you have an aftermarket horn with only one connection, then a relay is called for to make it blow!
Scott in CA
 
Sounds like a stuck on/off ground switch. I would check where you put your finger to sound the horn first, then work toward the horn for indirect grounds
 
BTW when I was having trouble with my horn circuit I hooked up a 12 volt bulb in its place - much less stressful to diagnose
 
Just another comment about the spridget horns. This is not related to your problem, but it came up with my car. The horn depends on a ground of the steering column to get the horn to work.
The design for the BE has the battery power wire go to the fuse box, through one of the fuses and then to the horn. The other connection of the horn then goes to the steering wheel contact on the plastic surround mounted on the dashboard. The spring loaded plunger on the steering wheel is connected to the push button. Soooo, (sorry for the long message) when the horn button in the steering wheel is pushed, the horn circuit is grounded to the metal steering column and there she blows! The ground depends on a good ground through the steering rack. Sometimes, as in my case, the lubrication of the rack and the ball joints did not allow for a consistent ground connection. I ended up running a wire from the steering rack to a bolt on the frame. This is needed when everything else is working OK, but the horn still no work.
Scott in CA
 
smaceng said:
I ended up running a wire from the steering rack to a bolt on the frame. This is needed when everything else is working OK, but the horn still no work.
Scott in CA
Click to expand...
I had to do the same thing with mine. Also had to modify the boss on my steering wheel (a Mike Lempert wheel) as it was touching the grounding ring on the column and blowing all the time. An hour or so with a Dremel cured the problem.

steering_wheel_hub.jpg
 
I would put a relay in there so the amp draw is not going to your switch use the switch run the coil in the relay and the contacts to run the horn, fuse all all power leads to the relay
 
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