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Intermittent Horn


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#1 RogerH

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Posted 17 February 2017 - 04:47 PM

Hi Folks,

              last night I noticed that the horn on my 4A worked when going straight ahead but did not work with the steering wheel at any other angle.

 

This morning I attacked the fault with my multimeter.

This showed that the fault was at the lower rubber UJ.  As you know there is quite a lot of car in the way - mainly the alternator.

After a short struggle the alternator was out. Another test with the multiumeter showed that the fault was definitely there.

Rather than break the steering shaft down I decided to put a link around the outside of the UJ.

 

When finished I pressed the horn button and .............Nothing.

 

On closer inspection of the upper UJ I found that the electrical link was broken (I wish I had found this before taking the alternator out,)

 I fitted another external link around the UJ - thankfully this now made a significant difference it now went .....toot.

 

How could the fairly large brass 1/4" ring connector break off. The UJ goes round but nothing else - how could it flex and break.

 

Roger

 


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Time is a drug - Too much will kill you
Forgive your enemy, but remember the ass-hole's name.
never surrender, never give up and always balance your butterflies

Veni Vidi Flati
TR4A - July 1967 daily driver         2010 RBRR No.22  2014 RBRR No.69
TR4 - March 1962 transforming like the proverbial caterpillar - it's now Royal Blue and now with the chromy bits.
 
 
 
 
 

#2 tim hunt

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Posted 17 February 2017 - 05:12 PM

Just forget these earthing links on the couplings Roger and fit a spring loaded contact as below to connect the upper steering column direct to the body. This provides a reliable constant earth for the horn and it's worked for me for 45 years!

TimAttached File  Horn earth to steering column.JPG   181.6KB   0 downloads
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#3 RogerH

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Posted 17 February 2017 - 05:18 PM

Hi Tim,

               yes, I have seen your previous posts regarding the slipping contact.

 

However I have problems with slip rings on dirty/rusty surfaces.

Although the 12V has a small current (100mA or so)  -  

are we confident that there is no microscopic arcing.

are we confident that this arcing is not causing microscopic cracking.

are we confident that the steering shaft (it is not a  simple mild steel) will not crack and fall in two.

 

Electricity goes down copper wires fixed contacts and that is where it stays (except when it breaks).

 

Roger


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Time is a drug - Too much will kill you
Forgive your enemy, but remember the ass-hole's name.
never surrender, never give up and always balance your butterflies

Veni Vidi Flati
TR4A - July 1967 daily driver         2010 RBRR No.22  2014 RBRR No.69
TR4 - March 1962 transforming like the proverbial caterpillar - it's now Royal Blue and now with the chromy bits.
 
 
 
 
 

#4 tim hunt

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    2007 Volvo V70 D5. Practical, but NOT a driver's car!

Posted 18 February 2017 - 10:44 AM

Ooer Roger, as a metallurgist (retd)you've given one more thing to worry about although the 50-year-old original steering column still looks fine to me.

Tim
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#5 RogerH

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Posted 18 February 2017 - 11:02 AM

Hi Tim,

          don't panic. It would take a fair bit of arcing and probably a decent voltage.

 

Just one of my foibles.

 

Roger


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Time is a drug - Too much will kill you
Forgive your enemy, but remember the ass-hole's name.
never surrender, never give up and always balance your butterflies

Veni Vidi Flati
TR4A - July 1967 daily driver         2010 RBRR No.22  2014 RBRR No.69
TR4 - March 1962 transforming like the proverbial caterpillar - it's now Royal Blue and now with the chromy bits.
 
 
 
 
 

#6 ianc

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Posted 18 February 2017 - 12:42 PM

The answer is to smooth the contact area to a very fine finish, then coat it with Vaseline.  This will ensure good contact and eliminate arcing.

Ian Cornish


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