[TR] TR4A horn

DAVID MASSEY dave1massey at cs.com
Thu Jul 12 06:08:07 MDT 2018

 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 DeLucaSent from my iPad** triumphs at autox.team.net **Donate: http://www.team.net/donate.htmlArchive: http://www.team.net/archiveForums: http://www.team.net/forumsUnsubscribe/Manage: http://autox.team.net/mailman/options/triumphs/dave1massey@cs.com
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