Horn short circuit

[ChicagoBob]

OK, I admit that I don’t understand my horn’s wiring. Actually, I don’t understand any wiring. If you use terms like “complete the circuit to ground,” or “the field collapses,” I have no idea what you are talking about.

My car is stock, 6V positive ground. My horn works well, but recently I noticed that the horn cover screw had disappeared. When inserting a new one (not too long, BTW), just as I touched the screw to the horn frame, straight in and to the hole in the frame, I got a spark, indicating a short circuit.

How could this happen? What is the horn frame connected to that would cause this? My horn works correctly, but I don’t understand how it can do so if the screw can short like that. Possibly the conduit is shorting to the wire connectors? If so, how can I prevent this.

I’m leaving the cover off until I can learn what’s going on with this.

 

[alexiskai]

The horn is one of the few electrical components on the A where power isn't supposed to flow back to the battery via the chassis (at least not initially). Instead, the connection is made via the horn rod. So the motor frame and cover shouldn't be live. My initial guess is that the live power connector is loose or is protruding in a particular way so that it's making contact with the cover, but if the cover and base are painted, it may not be able to short out. Or perhaps the contact is intermittent, or only happens when you tighten the cover down. Then the cover screw makes the connection from the cover to ground and you get the spark.

Can you send a picture of the way your wires are terminating at the horn?

 

[ChicagoBob]

Well, I can't send a picture. Never figured out how to do it on this site. However, I think you are probably right, in that the only way power could get to the horn frame would be from the connectors on the horn wires. Perhaps when I place the cover, the conduit slides up enough to contact one of the bullet connectors. Does that sound plausible?

 

[alexiskai]

Perhaps when I place the cover, the conduit slides up enough to contact one of the bullet connectors. Does that sound plausible?

If the connectors are placed correctly, into the sides of the terminals, surrounded by the insulating block, with no bare wire exposed, that should not be possible. See attached photos for correct connector placement (either connector can go in either terminal).

 

[rotorwrench]

A hot wire is directly connected to the horn at all times. I'm not sure what the replacement screw made contact with but what ever it was, it was hot. The screw grounded it. The screw may have been a bit too long or it didn't hit the threaded hole it was intended to.

 

[Tom Endy]

Look for the missing screw down in the horn somewhere. It may be causing a short. The screw is somewhat special. I would purchase a replacement from Bratton's.

The way the horn is wired one of the leads always has battery power on it and is connected to one of the horn terminals. The other lead runs from the other horn terminal to the button on the steering wheel. When it is pressed it puts ground to the other side of the horn and it ahoogus.

Tom Endy

 

[Herb Concord Ca]

If the wrong screw is used, the screw will touch a brush holder connecting it to ground.

 

[ChicagoBob]

If the connectors are placed correctly, into the sides of the terminals, surrounded by the insulating block, with no bare wire exposed, that should not be possible. See attached photos for correct connector placement (either connector can go in either terminal).

Good point. Mine isn’t connected that way. I’ll clean the paint out of those areas and try it.

 

[alexiskai]

Good point. Mine isn’t connected that way. I’ll clean the paint out of those areas and try it.

Not sure how bad your paint problem is, but just as an FYI, don't try to remove the screw between the two copper terminals (visible in my photo) if you're not ready to separate the horn bell from the motor base. That screw doesn't thread into the base, it goes through to the other side and tightens with a nut. So if you just unscrew it from the open side, the nut might drop off, which would be bad.