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Hi,

Today I got back my re-upholstered steering wheel. That got me thinking that this could be a good oportunity to fix a small issue I've been having.

Both steering wheel horn "buttons" work, but the RH side needs a lot of pressure to activate the horn than the LH side. Since both sides work, I don't think there's a problem with the rotary coupler. The main suspects are the switch assembly and the horn springs.

I unscrewed the RH horn mechanism, checked the springs and reassembled. Nothing suspicious there. I found out the horn is engaged when any of the 2 ball-point terminals, located at the underside of the moving part of the mechanism, make contact with the terminals located on the fixed part of the mechanism. Terminals were clean, but I sprayed them with contact cleaner to be sure. Also, both screws have a fixed travel, so it's not a matter of calibrating the spring travel.

I also inspected the switch assembly circuit. Traces look good. Tested for continuity on the horn trace (each side has an independent trace). Since I'm a noob with the multimeter, I don't know what other relevant readings I should get while I'm at it. Any recomendations ? Checking for resistance gave me weird readings.

Apparently the previous owner lived with this issue for a long time, since SW airbag module had a big crack from top to bottom, all along the RH horn "button". I don't know if this was a consecuence or cause for this problem. I replaced the airbag module and the problem is still there.


So, what do you think ? I'm quite puzzled. Before attempting this fix I suspected the cause might be a cracked spring base, or a busted spring, or even worse, broken traces in the circuit, but none of that was true. Everything seems fine, but my RH horn "button" still is a pain to use.

Help please !

Here are a couple of reference pics.

N.

[attachment=3:1wrsgrut]IMG00046-20100218-1736.jpg[/attachment:1wrsgrut][attachment=2:1wrsgrut]IMG00047-20100218-1736.jpg[/attachment:1wrsgrut][attachment=1:1wrsgrut]IMG00048-20100218-1736.jpg[/attachment:1wrsgrut][attachment=0:1wrsgrut]IMG00049-20100218-1736.jpg[/attachment:1wrsgrut]
 

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Checking for resistance gave me weird readings.
This is one clue for me, the blind rivet connections between the printed circuit and the metal work each side is the other.
I suspect the electrical connection via the RH rivet is high resistance, but varies, which explains the 'weird readings'. When you press the RH button hard enough the metalwork moves enough to get a better connection.

How to fix?
I don't really know - you could try contact cleaner as a temporary proof of concept test - but this might not work anyway.
You could try drilling out the existing rivet and replacing it, either with another rivet or with a threaded screw. It depends what you have available, and there is a risk of damaging the printed circuit.
You could try giving the rivet a sharp smack with a centre punch, either in the hole or in say three places on the collar. If the rivet is into an aluminium casting, just be careful how much power there is behind the hammer blow. I'd use the three lighter blows on the rivet collar myself, probably with an automatic centre punch.
The other alternative is to clean off the surface of the track, and maybe the side of the contact ball-point, and solder a piece of light wire between the two. IE, provide an alternative connection path.
As I say, the chosen fix depends on what resources you have, and that includes your own skill area.

Good Luck
 
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