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Horn constantly on


Darron
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Need some help ,so went to change my steering wheel tonight ,the boss was a pig to remove but got there in the end,  put it all back, and reconnected my horn push everything fine just leveled up the badge in the middle then it happened the horn went on constantly which was a pain as i live in a close everyone was out looking as i tried to disconnect the battery, so now the horn will not turn off, no boss on the column so no connection there any ideas would be appreciated

Darron

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Hi Andrew 

wheel boss is completely removed so must be something inside the column that’s touching and earthing Will have to remove the column tonight and check it out , thanks for the reply 

Darron

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yes  thats right the horn is fed with a permanent live via a mauve wire to one of the two horn terminals the second terminal is the earth , 

this runs through the harness up to the steering column  just under the dash is a bunch of bullet connectors for ligts indicators and horn .

from here up to the contact ring on the column switch cowl  this is were the pencil brush makes contact with the horn push  if the new handwheel boss is touching the column ring it will complete the earth and thar she blows , as the stg column is collapsible it can move as andrew says given a good firm pull and wiggle the shaft can rise upwards or you can push the column tube downwards to make a decent gap

the earth is continued down the inner column has a wired across the UJ and a earth from the rack to the chassis/engine ....its a simple system but take a tortuous   earth route 

next time it blows just pull the wire off the horn , 

Pete

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Thanks Pete 

will check to see if there is a snag on the wire up to the brass ring tonight and disconnect from the bullet connector first save the embarrassment of the horn 🤣

thanks guys

Darron

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Ha ha already thought of it thanks Pete and I’m sure the close will be appreciated of it as well ,I’m sure it sounded for only a minute or two last night at 8 o’clock but with the Panic it felt like ten minutes 😩

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Just a quick update on horn sticking to those that replied ,it was totally self inflicted when I changed the steering coupling a few days earlier I managed to trap the purple and black horn cable under the washer on the top column mounting 😩and me banging on the steering boss must have been enough to short through the wire , lesson learned,so thanks again for the replies 

Darron 

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  • 3 weeks later...

Hello Guys,

I have a similar problem with the horn not working after replacing the steering column bushes.

The horn was not working prior to the above being completed. The issue has been traced to the push button area someone earlier has played around with the horn push by means of making up a metal plate under the button section followed by the brush section being made up with a closed wire contact. This just doesn’t work although I can make the horn work continuously with the horn in place.

I have concluded the fault is within the press button area as I can short out the horn as working by means of shorting out to earth from the brass ring. I have no reference within the horn push area as there is next to no spring back within the horn push

 

Best regards

Brian

image.jpg

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The horn works by earthing the system and on original horn pushes there's a metal strip which contacts the end of the pencil. Handy if you're using the original steering wheel but not if you use an aftermarket version.

image.jpeg.9562a122d99711c1b64858d7e97b36e7.jpeg 1767583004_ScreenShot2020-08-09at10_42_51.jpg.38d64fa6596beab9622c83cd248b2fd9.jpg

It doesn't really affect anything if you make up a flexible connection from the centre button to the horn pencil; I have it on my own system, with a ring terminal rivetted to the centre of the push mechanism then a short wire soldered to the end of the pencil. Provided it's done properly it won't change the operation of the push button. The other part of the connection is just visible in the photo, the spring that completes the circuit. You need both or nothing will happen. The horn push itself is just a plate but the spring sits proud of the outside of the button assembly and makes contact with the steering wheel itself, so when you push the button you complete the circuit. I don't see any spring, or secondary contact, on yours to complete the circuit?

 

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Hi Colin,

Thank you for your prompt post.

Yes it is an aftermarket steering wheel for my 74 TR6. I have taken another photo of the horn apart, you will see I increased the centre contact point with solder. The spring is rather poorly made up, can you recommend a part to purchase or does this have to be made up?

Thanks BRIAN

image.jpg

image.jpg

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Hi All,

Unfortunately I am still having horn function issues.

Current update:- purchased replacement horn assembly for a Tourist Trophy or Motalita steering wheel. My wheel appears a clone wheel as the replacement horn plastic perimeter had to be reduced by at least 1mm in order to fit the boss. The back of the horn had a spade terminal in order to have an hard wire contact to the brush contact assembly. This will initially allow the horn to operate correctly until the steering wheel is rotated. I’ve traced the problem to the brush contact slipping out of the horn boss contact hole.

One other issue being the metal contacts around the perimeter of the horn assembly which I believe secure the unit to the boss and give a final earth contact, 75% of the metal had to removed in order to install to the boss however good earth contact was maintained. 

I believe my issue is not being able to maintain sufficient contact with the brass ring contact surface - open to any advice on this one or if anyone else has had a similar issue.

 

Best regards Brian

 

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If the horn pencil is slipping up through the wheel then glue it in place, as far down as the plastic outer will allow without fouling. The spring-contact will then be held tight to the brass ring, and you can adapt the contact at the other end as required to reach the horn push mechanism.

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Superglue is a bit harsh; try any kind of sealant or mastic that will enable you to remove the pencil again without having to drill it out! Evostik or Bostik would be my choice or even silicone sealer. I don't think anything was used originally, it was just a tight fit and didn't move about between the two contacts.

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22 minutes ago, Brian Sculpher said:

 have you any idea what was done originally?

What was done originally was to use a "horn pencil" that was correctly dimensioned for the steering wheel, so that the horn push boss held it in place with the sprung end pre-loaded against the slip ring. If yours is moving up far enough to release the spring pre-load then it's too short.

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2 hours ago, NonMember said:

What was done originally was to use a "horn pencil" that was correctly dimensioned for the steering wheel, so that the horn push boss held it in place with the sprung end pre-loaded against the slip ring. If yours is moving up far enough to release the spring pre-load then it's too short.

Non-original wheel and boss, so it can't press against the terminal as the original would. As we can't brace it against the top of the travel we'll just have to make sure it stays lower down where it contacts the horn ring.

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bit late but on you early photo you have that pencil wired on the wrong end of the pencil 

the sprung end runs on the slip ring the fixed end (with a dab of solder) should be uppermost 

only one end is sprung as a plunger to run on the ring ,  there are two lengths of pencil available  a normal and a longer 

Pete

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