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Horn fuse keeps blowing


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Hi Team..

Ever since completing my 73 build with original wiring my horn fuse kept blowing. Haven't worried about it until our Warrant of fitness check every 6 months where I replace it for the check. Horn goes fine until I discovered it only blows when I turn my headlights on. I know from the wiring diagram it is linked to the cigarette lighter and wondered if it has anything to do with the bulb that is on inside the cigarette lighter which is definately going when lights are on. Is there anything I can easily check k without pulling the dash. Cheers Steve NZ

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Better get under the dash and inspect the harness. I had similar gremlins and found some wiring insulation significantly melted. 

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[align=left]Jeff T.

 

When I die I want to die like grandpa, peacefully in my sleep... not screaming, like his passengers. [/align]

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It may just be coincidental that the fuse blew when the headlights were on. There really isn't anything that the light on the lighter could do to pop the fuse. Have you tried plugging in the lighter when the headlights are on, to see if that blows the fuse? Have you disconnected the horns and pushed the horn button with the horns disconnected? To me the two most likely causes of the fuse popping are the horns shorted internally or the wiring in the steering column being pinched. 

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“If you can't explain it simply, you don't understand it well enough.”

--Albert Einstein

 

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Hi eveyone. 

Thanks for the replies. Sorry I was away over the weekend and didnt get an email notification. 

I fitted a new horn (CJ Pony) and also fitted a new steering wheel when I assembled the car. Had no steering wheel parts left over so I will have to get an auto electrician to investige those as a possible cause or a short but it seemed co-incidental the horn works fine for days it is only when I put the headlights on it blows. Cheers

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  • 2 weeks later...

some cars ground the horn button to the steering column to make it beep (ours does not!). Some aftermarket horn buttons have a wire spring to short it out that has to be clipped off to use on a 71-73 mustang. I had the same problem with mine and had to clip the spring off and then use electrical tape to insulate the bare parts of it from the very close steering wheel nut.

 

Edited by jspears
clarity
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On 3/1/2021 at 3:09 AM, Ballaratcastle said:

Hi eveyone. 

Thanks for the replies. Sorry I was away over the weekend and didnt get an email notification. 

I fitted a new horn (CJ Pony) and also fitted a new steering wheel when I assembled the car. Had no steering wheel parts left over so I will have to get an auto electrician to investige those as a possible cause or a short but it seemed co-incidental the horn works fine for days it is only when I put the headlights on it blows. Cheers

Hi 

I had same problem after fitting a very expensive 5 ply steering wheel by Volante. Also exaserbated by the fact that one of the two old Ford horns had gone short circuit. 

My solution was to use the run out from steering wheel to control a 12volt relay and let the relay carry the current and not the steering wheel.  The old horns draw about 6 amps - and the switch in the wheel I wouldnt trust with 1Amp. I ran a separate in-line fused feed to the switch side of the relay from the battery. The coil of the relay is fired by the steering wheel with only 230mA going through the old circuit path in the harness. This circumvented all the wiring issues and trying to stand on your head in an attempt to deal with the dumb-ass location of the fuse cluster under the dash . 

 

 

relay.jpg

drivers.jpg

Edited by 1sostatic

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Enjoy's searching out 71-73 history

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