Subject: [TR] TR4 Horns not working. I need a suggestion

From: "Daehler, William F" <[email-masked]>
Date: Wed, 11 Jul 2012 19:29:28 +0000

My horns have stopped working.   They had working fine when I put in the new
wiring harness five years ago.

I started troubleshooting last night, and found that I do have 12 V going to
the one terminal to each of the horns. Unfortunately I have 12 V going to the
other terminals too!

There must be a short somewhere, but my battery doesn't go dead all the time.
That's fine.

I did a little more experimenting.  I disconnected one of the leads from the
horn (the purple and black wire that is supposed to be grounded).  Then I took
a jumper wire with alligator clips, and ran it from the free tab on the horn
to a  true ground.  The horn worked fine! Toot, toot !  I repeated this on the
other horn, it worked too. Toot, toot.

Then I took off the horn switch on the steering wheel, measured the incoming
voltage, checked that the metal steering column was Zero volts, and checked
the operation of the switch, nothing wrong there.

It seems like the ground path is going hot, but the battery isn't going flat.
Puzzling.

Any suggestions?

Will Daehler
63 TR4  Powder Blue
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From: Randy and Valerie DeRuiter <[email-masked]>
Date: Wed, 11 Jul 2012 16:18:43 -0500

Hi Will-

Take a look at a TR4 wiring diagram if you have one handy - the horns do
ground through the horn button - eventually via the steering column/steering
rack.  If you want to keep experimenting, take your alligator clips and ground
the metal steering column inside the engine bay, just before the uppermost
rubber coupling.  With it grounded, try your horn button - if it toots, you
are loosing ground through the column as it goes to the rack - work your way
down if needed to find the fault.  If it doesn't work, you are losing ground
possibly at the horn ring, you could find where the purple/black wire goes
into the steering column and check there first, if good its something going on
with the horn ring/horn pencil/horn button.

Randy
ps.  Nice to meet you at the Mitty! (red TR4..)

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From: "Randall" <[email-masked]>
Date: Wed, 11 Jul 2012 14:55:55 -0700

> There must be a short somewhere,

What you have is more of a "long" than a short.  A broken wire or bad
contact, somewhere.

My next step would be to check at the horn button again, with a jumper
across the contacts (ie terminal to steering column/shaft).  Only the horn
uses the shaft as a ground, so without that connection you cannot tell if
the shaft is grounded or not.

If the shaft comes up to 12v, it will likely be either the ground connection
at the steering rack, or the jumper across the rubber coupling in the
column.

-- Randall

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From: "Greg Gelhar" <[email-masked]>
Date: Wed, 11 Jul 2012 19:18:58 -0500

It is not that both sides of your horn are going plus 12 volts, you are just 
reading through the horns windings. You know the problem. Your not getting a 
switched ground from the horn button. The horn ground depends on a jumper 
around the rubber flex couplings on the steering shaft. Check to make sure 
the little wire bridging those couplings are intact.

Greg G.
Osseo, MN