Go Back   The Ford Barn > General Discussion > Model A (1928-31)

Sponsored Links (Register now to hide all advertisements)

Reply
 
Thread Tools Display Modes
Old 09-04-2022, 03:00 PM   #1
ChicagoBob
Senior Member
 
ChicagoBob's Avatar
 
Join Date: May 2010
Location: Yorkville, IL
Posts: 126
Default Horn short circuit

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.

Last edited by ChicagoBob; 09-04-2022 at 03:08 PM.
ChicagoBob is offline   Reply With Quote
Old 09-04-2022, 03:19 PM   #2
alexiskai
Senior Member
 
alexiskai's Avatar
 
Join Date: Apr 2018
Location: Mebane NC
Posts: 2,318
Default Re: Horn short circuit

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?
alexiskai is offline   Reply With Quote
Sponsored Links (Register now to hide all advertisements)
Old 09-04-2022, 04:45 PM   #3
ChicagoBob
Senior Member
 
ChicagoBob's Avatar
 
Join Date: May 2010
Location: Yorkville, IL
Posts: 126
Default Re: Horn short circuit

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?
ChicagoBob is offline   Reply With Quote
Old 09-04-2022, 07:17 PM   #4
alexiskai
Senior Member
 
alexiskai's Avatar
 
Join Date: Apr 2018
Location: Mebane NC
Posts: 2,318
Default Re: Horn short circuit

Quote:
Originally Posted by ChicagoBob View Post
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).
Attached Images
File Type: jpg IMG_4549.jpg (59.8 KB, 26 views)
File Type: jpg IMG_4550.jpg (52.0 KB, 24 views)
alexiskai is offline   Reply With Quote
Old 09-04-2022, 07:49 PM   #5
rotorwrench
Senior Member
 
rotorwrench's Avatar
 
Join Date: Jun 2010
Location: San Antonio, Texas
Posts: 16,346
Default Re: Horn short circuit

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.
rotorwrench is offline   Reply With Quote
Old 09-04-2022, 08:19 PM   #6
Tom Endy
Senior Member
 
Tom Endy's Avatar
 
Join Date: May 2010
Location: Southern California
Posts: 3,119
Default Re: Horn short circuit

Sponsored Links (Register now to hide all advertisements)
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
Tom Endy is offline   Reply With Quote
Old 09-04-2022, 11:00 PM   #7
Herb Concord Ca
Senior Member
 
Join Date: May 2010
Location: Concord CA
Posts: 622
Default Re: Horn short circuit

If the wrong screw is used, the screw will touch a brush holder connecting it to ground.
Herb Concord Ca is offline   Reply With Quote
Old 09-05-2022, 09:38 AM   #8
ChicagoBob
Senior Member
 
ChicagoBob's Avatar
 
Join Date: May 2010
Location: Yorkville, IL
Posts: 126
Default Re: Horn short circuit

Quote:
Originally Posted by alexiskai View Post
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.
ChicagoBob is offline   Reply With Quote
Old 09-05-2022, 10:52 AM   #9
alexiskai
Senior Member
 
alexiskai's Avatar
 
Join Date: Apr 2018
Location: Mebane NC
Posts: 2,318
Default Re: Horn short circuit

Quote:
Originally Posted by ChicagoBob View Post
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.
alexiskai is offline   Reply With Quote
Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump

Sponsored Links (Register now to hide all advertisements)


All times are GMT -5. The time now is 04:28 AM.