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EFV-8 Club Forum / General Ford Discussion / horn short circuit?

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Posted By Discussion Topic: horn short circuit? -- page: 1 2     MICHV8 05-07-2020 @ 11:05 AM reply profile send p.m. Member Posts: 444 Joined: Jul 2010 If a horn sounds with only the power wire and no ground wire and the horn bracket is insulated from the fender, does that simply mean an internal short in the horn itself? update: the horn works fine when off the car with an external battery... only works with either wire combination touching + and - posts. BUT when on the car, the horn sounds when one of the horn wires is touched to 15Y power (from new headlight harness 40-11646) and doesn't sound when the other horn wire is touched to the same 15Y, but gives a quick spark. Is this a wiring harness short? This message was edited by MICHV8 on 5-8-20 @ 8:48 AM PowerSerg 05-08-2020 @ 10:37 AM reply profile send p.m. Member Posts: 2 Joined: Jun 2019 what year and model of car do you have? is it positive ground or negative ground wiring? TomO 05-08-2020 @ 10:54 AM reply profile send p.m. Senior Posts: 7256 Joined: Oct 2009 I am assuming that you are working on your 36 roadster. You will need an ohm meter to check this out. Your horns should be isolated from ground and the yellow wire should have 6 volts on it. The horns should blow when the horn button completes the circuit to ground via the blue wire with a yellow tracer. I don't know what wire 15Y is connected to. Use the color codes on t6he wiring diagram to describe your problem. Tom CharlieStephens 05-08-2020 @ 12:02 PM reply profile send p.m. Senior Posts: 893 Joined: Oct 2009 The horns are not isolated from ground, they bolt directly to the chassis (which is ground). The current comes into the horn and then out through a wire that goes to the horn button where it is grounded. Charlie Stephens This message was edited by CharlieStephens on 5-8-20 @ 12:03 PM MICHV8 05-08-2020 @ 2:18 PM reply profile send p.m. Member Posts: 444 Joined: Jul 2010 Charlie Stephens, This is a 34 whose horns have 2 wires...one receives power from 15Y and the other receives ground from 12Bl-Y which is the horn button circuit at the bottom of the steering box. My horn is not connected to 12Bl-Y, but sounds when one wire is touched to 15Y. So the question to me is, where is the horn getting the ground when it is on the car? I have isolated the horn bracket from the headlight bracket with a gasket. i also put a rubber washer on the bolt under the fender that secures the horn bracket to the headlight bracket...still the horn sounds with no ground wire attached. So the million dollar question to me is, where is the horn getting the ground? The headlight bracket has the normal stock rubber pad ... Tom(), 15Y is the main power from the starter switch battery side I had initially assumed that my steering column horn wire was grounding so I started testing without the horn ground circuit (12Bl-Y) and discovered the current situation CharlieStephens 05-08-2020 @ 2:33 PM reply profile send p.m. Senior Posts: 893 Joined: Oct 2009 What you are describing shouldn't be happening unless someone rewired the horn in which case I would expect to see only one wire going in and the horn itself being grounded. I am sorry to say I have no suggestions. Are there any local EFV8 Club members that could stop by and maybe spot something? Charlie Stephens This message was edited by CharlieStephens on 5-8-20 @ 2:36 PM MG 05-08-2020 @ 3:23 PM reply profile send p.m. Senior Posts: 1260 Joined: Nov 2009 1934 Ford Wiring Diagram: MICHV8 05-09-2020 @ 10:38 AM reply profile send p.m. Member Posts: 444 Joined: Jul 2010 positive ground thanks MG...matches the schematic that came with the harness It seems to me the fender or fender brace is somehow providing ground, but I sure don'e see how. I've even tried wrapping the horn bracket bolt threads with electrical tape where the bolt runs through the headlamp bracket and still same problem...horn sounds with no ground wire attached. Even took horn apart and everything looks ok...mystery. 37RAGTOPMAN 05-09-2020 @ 11:39 AM reply profile send p.m. Senior Posts: 1962 Joined: Oct 2009 HI MICHV8 how about a few photos I think all FORD horns had 2 wires, in the 1930's my 37 has 2 wires,and I Have 2 horns, I have never saw a horn with a internal short, but I guess anything is possible, are you sure to have original Ford Horns and not a repros ? let see a photo of the inside of the horns,wiring connections. using a volt meter you should be able to tell where the short is my 2 cents 37Ragtopman like they say a photo is worth a 1000 words, MICHV8 05-09-2020 @ 1:03 PM reply profile send p.m. Member Posts: 444 Joined: Jul 2010 37ragtopman... The horn works fine off the car, so a horn internal problem not a candidate, right?

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