[alfa] Old wheel on newer spider (longish)

[Mark Denovich <mark@xxxxxxxxxxxx>]

I wanted to put a steering wheel (Personal) from my old '76 Spider onto 
my new '86 Spider.   Everything is straight forward except for how to 
deal with the horn.

I was going to ask if anyone else solved this problem, but I engineered 
a solution before I ever got around to posting it.   When I searched the 
digest I found at least one other soul had tried it, and had the same 
question (but no answer) so I'll post my solution here.

I will say before I get into the details, that the different steering 
wheel completely transforms the feel of the car.   The small Momo Monte 
Carlo wheel made it feel go cart like, with a rather heavy feel.   Much 
more aggressive than other Spiders I've driven.   The uprated suspension 
and tires add to this feeling.   The much larger old wheel results in a 
much lighter feel.   This is what I wanted when I initially bought this 
car, but I must admit I got used to the heavier feel.   I'm sure I'll 
just have to get used to this one.  It certainly looks gorgeous.

Now the How-To:

Unlike the '76 where a positive lead is threaded up through the steering 
column, the '86 has a copper stud that contacts a brass ring supplying 
12V+ to the horn button.   The horn button completes the ground path, 
thereby energizing the horn relay and sounding the horn.

The problem is that the '76 has this metal disc which is grounded, and a 
three spoke horn mechanism (which is positively charged).  When the 
spoke levers are depressed the positive hub contacts the metal disc and 
completes the circuit.   The problem is that if you just try and install 
the steering wheel as is, the backside of this metal disc will contact 
the copper stud found on the '86, making the horn on all the time.   Not 
good.

The Momo hub I had, had a plastic disc, with a brass ring that was 
designed to contact the copper stud.  I'm guessing this is the stock 
unit fitted to the Momo hub, but I can't be sure.  Sorry if it isn't 
because this is a vital part of the solution.

I took this plastic disc, cut off the protrusion that the ground wire 
goes through, and made a notch for the wire to fold back into to the 
center of the disc.

I removed the cir clip holding the metal disc onto the old wheel.    I 
cut a small 5mm square notch into the center of the disc.   This lets 
the wire from the brass ring pass up through a hole in the wheel.   I 
then reinstalled the disc upside down...  if you do it right side up 
there won't be enough room between the plastic disc/brass ring and the 
plastic steering column shrouds.

I then used some double stick foam tape to secure the plastic disc to 
the metal disc.   I then soldered the wire from the plastic disc to the 
red wire that connected to the three spoke horn mechanism.

Bolt the steering wheel back on, and voila... old wheel, new car, and 
functioning horn!

--Mark
The Alfa Wiki: http://alfa.denovich.org
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