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Horn fuse blowing

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More electrical gremlins on my 73 cr tr6!   My horns stopped working  and  I found the fuse  -35 Amp had blown. I replaced this and all was well. I checked for any obvious wiring issues and found none. On taking car for MOT I checked horn on the way and found fuse had gone again! I replaced fuse just before reaching the MOT station and it lasted for the test however by the time I got home the fuse had gone again!

This fuse covers the horns,all interior lights and the headlamp flasher. All bulbs on interior lights (underdash, boot) are not fitted at the moment. the glove box bulb operated ok when I earthed it (Switch missing). The interior light switch is not fitted at the moment and connections are insulated.

So far I have checked  that the circuits from the fuse are not showing a leak to earth by  putting a test lamp on them with a feed  directly from the Pos battery terminal. I have also checked that the horn push is ok by  removing  the trigger connection from the relay and using a test lamp. I  have taken apart the Lucas relay  and could find nothing  wrong and no sign of shorting. I have checked all the bulb holders and no sign of shorts. The headlamp  flasher operates correctly( new switch). I have been unable to replicate fuse blow in the Garage even with ignition on and lights. Before  I start an autopsy  on my wiring loom, has anyone had the same problem?

I must be missing something !!! Any words of wisdom as ever,  very gratefully  accepted !! 


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It normally shorts out top section of the stearing coloum, as you move the stearing wheel it shorts out blowing the fuse, I have had smoke coming out of mine,

I would lower the fuse,

It became such a problem I used thinner cables on relays this allowed a permanent fix,

Hope this helps , pink 


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Hi mak,

normally when the steeing wheel boss is moved forward the horn may well sound.


Have you tried removing everything from the dodgy fuse except the horn and then driven it.

Swap the various services and see which one pops the fuse.



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1 hour ago, MARK said:

Thanks for your reply Pinky. I think the horn switch is to earth and so a short in the steering column should trigger the relay and cause  horns to sound.

Am I right anyone?


You are right, however on that fuse line is the lights etc open it up and have a look, that's what probably,is shorting out and blowing the fuse


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Thanks as ever Rodger  for your  words of wisdom !!!!

Going to try that next but got a broken front spring at moment and trying to source of 10% uprated  slightly lowered to match the recently fitted rear springs !

wishing that I had replaced whole wiring loom instead of  just the rear! Hindsight is a wonderful thing.!



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  • 1 month later...

Finally solved the horn / interior light fuse blowing !! The  power feed  wire  to the head lamp flasher terminal on the column dip switch has been rubbing against the indicator cancellation ring on the column and has been occasionally shorting !!! Hence I could not replicate the problem in my garage as it was only going to happen when the steering wheel was well rotated !!!

ELECTRICAL GREMLINS ON OLD CARS !!  Rather satisfying when you beat the  little beggers though!! ( Fingers crossed and touching wood !!!!)


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