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Hella horn -troubleshooting


rapandi
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Hi team,

 

I am trying to work out how many horns are connected to a 2002. I am referring to a factory set up. My 72tii has 2 horns (one not working) while my friends 74tii had only one. 

 

Any idea why the difference? 

 

Can these horns be fixed if not functional? 

 

Raj

 

this is mine on right side

DSC_0295.thumb.JPG.1a4ef941115c6136fb916ff90068f8e7.JPG

 

Left side

 

DSC_0300.thumb.JPG.d78f1747cb69e67b8bcdd49473fcef7a.JPG

 

My friends single horn 

 

 

IMG_2771.thumb.JPG.d7b9ae5516851c07d91dc88febf4b9d2.JPG

 

 

 

 

 

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I think the early cars had two and later were rationalised to one. Definitely been discussed here before. 

 

First case is check the relay. Mine has the cylindrical relay and I have found that if it hasn't been used for long while it would stick and not close the contact. A sharp rap with a screwdriver handle fixed it up on the two occasions it has needed it. 

 

Check there is a voltage at the horn when operated. This proves the relay is working.  Check the ground too (at the voltage regulator I think). 

 

The horns are electromagnetic so can be cleaned and adjusted , if you can open them up. They might have an adjustment screw on the back which may be worth playing with to see if you can get a squeak out of them. 

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Think the Roundies had "round" horns and not flat. Looks like a nautilus shell.

 

check input and output voltage at the Hella relay near the bulkhead. I mixed up two wires on my 69. Reversed them and now both horns work.

 

if you are careful- test the horn by quickly applying 12v from a battery to see if it sounds. Don't apply power for too long as the diaphragm may be damaged.

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The subject of horns is interesting.

D.Martijn (in his Touring restoration blog) posted these pics of the horn washers.

58fceaffa131d_HornWashers.thumb.jpg.be7effc6528fef55a624943316487246.jpg

 

Recently I had refitted my horns and noted the metal mounting brackets were actually a set of 3 pieces per bracket and one in the set was stamped as shown in the below pic (one for lo tone, & one stamped for hi tone).

DSCN2853crsm.JPG.b59b10880d80ce30e138bddf394ddf84.JPG

 

The BMW Blue Parts Book shows the item 1 horns as "special equipment", so, I guess you got the round horns unless you special ordered????

26.png.da75df7456b0cd30c535b81e5f08de60.png

 

 

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Roundie 2002s (at least US spec cars) had 2 "seashell" horns (I think 1600s only had one, can someone confirm?), while squarelights only had one flat horn (like those used on VW Beetles).  That was another moneysaving dodge the factory used to keep prices down during those days when the D-mark was rapidly appreciating vs the dollar.  

 

Those round horn relays used on roundies are NLA, but if you're careful, you can bend back the crimped-over edge of the cover, remove it and clean/file the points if they're stuck or not making contact.  Of course if you're not looking for originality most any relay with the correct number of contacts will substitute.  

 

As Simeon pointed out, there's an adjustment screw on top of the seashell horns, and on the back side of the flat ones.  Connect the horn directly to power, and slowly turn the screw in (or out) until it starts honking.  If the adjustment doesn't work, then the internal vibrator coils are shot...and so is the horn.

 

mike

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