[TR] TR4A horn

Greg greg at gregoryd.com
Thu Jul 12 18:35:24 MDT 2018

I’ll add my experience to the mix: the horn on my ’67 TR4A would not work consistently. It would work, but randomly, it seemed. I examined all of the things Dave mentions, tested the wiring, and replaced the relay and the fuse. None of it worked.


The issue ended up being with the contacts pictured below (and here: https://imgur.com/n5mieHF), which bring the circuit up to the steering wheel and from there to the horn push:



Over the years, these contacts had worn down to the point that the steering wheel did not make constant contact with one or the other. 


I discovered that, if I pushed on the horn and also pushed the steering wheel laterally just a bit to the left towards the driver’s door, or to the right towards the passenger door, contact would be made and the horn would sound. And it worked consistently – it still does.


If nothing else is fixing it, try the left or right push. Having the engine on helps.


I’ll take this opportunity to ask my own question: does anyone have a recommendation for how to improve the contact “permanently”?  Something like a silver conductive epoxy? If the contacts were maybe a millimeter larger in the direction of the steering column, the left/right push probably wouldn’t be necessary.


One other thing: sometimes the circuit would complete – you could see it on the ammeter, but still no horn. That took a turn or two on the adjustment screws on each of the horns.





From: Triumphs <triumphs-bounces at autox.team.net> on behalf of DAVID MASSEY <dave1massey at cs.com>
Date: Thursday, July 12, 2018 at 8:30 AM
To: <john-marie at sbcglobal.net>, <triumphs at autox.team.net>
Subject: Re: [TR] TR4A horn


There are a number of things that have to work right for the horn to work reliably.  Power to the horn relay comes from the fuse but the grounding of the other side of the coil runs through a number connections that are the usual culprits in cases like these.  


First off there is a slip-ring behind the steering wheel.  This is the conductor the horn brush contacts and provides a current path as the wheel turns.  If there are dead spots (dirt, corrosion, damage) the horn brush cannot make good electrical contact and the horn will not work.  


The other end of the brush contact the horn push (push-button switch) in the wheel center.  That switch can also be bad but usually it is not dependent on steering wheel position.


The other side of the push contacts the steering wheel and hence the steering wheel shaft.  But we are not done since the steering wheel shaft is not ground.  The shaft rotates in a couple bushings which may or may not make contact to the outer shaft housing.  Also, this shaft connects to a second shaft via a rubber coupling.  And this shaft connects to the steering rack pinion shaft via another rubber coupling.  AND the rack itself is mounted with rubber bushes.  The designers, in an effort to make a reliable ground connection for the horn push, added grounding straps at each of the steering shaft couplers and to ground the rack.  If any of these straps is missing or broken you will not have a reliable ground connection to the steering wheel.


You can see these all depicted in the Moss catalog 



Good luck.




Dave Massey



-----Original Message-----
From: John Deluca <john-marie at sbcglobal.net>
To: triumphs <triumphs at autox.team.net>
Sent: Wed, Jul 11, 2018 10:12 pm
Subject: [TR] TR4A horn

My TR4A horn blows, but not consistently. With the front wheels off the ground, holding the horn button down and turning the steering wheel stop to stop, horn blows but not continually. There are dead spots where it doesn’t blow. But the dead spots are not always at the same place. Any ideas as to what is the cause? John DeLuca Sent from my iPad ** triumphs at autox.team.net ** Donate: http://www.team.net/donate.html Archive: http://www.team.net/archive Forums: http://www.team.net/forums Unsubscribe/Manage: http://autox.team.net/mailman/options/triumphs/dave1massey@cs.com 

** triumphs at autox.team.net ** Donate: http://www.team.net/donate.html Archive: http://www.team.net/archive Forums: http://www.team.net/forums Unsubscribe/Manage: http://autox.team.net/mailman/options/triumphs/greg@gregoryd.com 

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