RS steering wheel
This isn't as easy as it sounds. There is the old wheel to remove, an airbag to get rid of and then some electrical issues to deal with to get the new horn working. You will also need 964 cowling and a few other bits.
First of all turn your alarm off depending on what you have.
Always disconnect the battery before playing around with airbags. They are explosive devices and you don't want them going off in your face. Leave the car for an hour afterward to be on the safe side.
At the back of your regular OEM 993 airbag wheel you have 2 holes
And if you peek inside you can see a star headed screw
Undo these using a suitable bit and a shortish screwdriver so it doesn't foul the dash
This will release the airbag. Pull it gently outward and disconnect it pulling off the red connector.
Get it safely out of the way.
Now loosen that large nut (24mm from memory although i could have that wrong) ... don't lose the spring washer behind it. You can then pull the whole wheel off.
Loosen the 4 screws that hold the front of the cowling in place and remove as well.
Then you'll have the clock spring which can also be taken off carefully. Keep it intact though because if it comes apart it gets very messy very quickly.
The clockspring has a little connector on the back which goes down into the dash and connects up with 2 orange plugs, one of the airbag and one for the horn.
Now attack these small cross head screws at the sides.
Release and undo the 993 cowling.
Now we need to fix 2 things:
1. airbag warning light (which will be permanently on if no airbag is connected)
2. the horn circuit which is no longer wired through the clockspring because the clockspring is no more
To perform these 2 you need to find the 2 orange connectors behind inside the dash whish were also attached to the wiring coming out of the clockspring.
You will need to make 2 custom pieces of wiring up that mate onto the 2 orange connectors that were inside the dash. The way I did it was to butcher the female connectors on the clockspring although thats probably not the best idea if you intend selling the whole steering wheel on.
Firstly on the horn connector you have a white and brown wire which needs to be reused. On the end of this I soldered a small hollow circular terminal. More on this later. The other wire which normally completes the horn circuit becomes redundant because the new horn circuit will complete through a slip ring that sits around the steering column.
Now lets look at the airbag side of things.
On the second airbag connector I made a simple loop out of the orange clockspring-side female plug and inserted a 2.8 ohm resistor in there which is what will fool the car into not giving out a warning.
Now onto the 964 cowling. You will need this as the original 993 cowling does not allow proper flush fitment of the RS steering wheel boss. Its fairly simple to fit round.
Here is the steering column with the new cowling fitted. Note where the arrow is there is a small hole and 2 locking pinholes.
You will need the 964 horn contact plate to go in there . This is only a few pounds - 964-652-104-00. Just push it firmly into that hole so that it sits flush.
Like that (cowling now removed just to confuse you !)
Now lets finally look at the wheel and work out how the horn circuit all works so that when you push the button on the soft pad you get noise.
Looking at the back of the RS wheel boss you can see a gold metal ring. The horn contact plate you have just pressed in place will brush against that when in use.
Now look again and you will see a stubby metal tab that protrudes from the base.
This connects up with the earth by rubbing against a slip ring down in the depths of all those circlips and washers, rings etc.. on the steering column.
To make this easier to get, here's my funny diagram:
So you have 2 wires emanating from inside your wheel boss. One originates from the horn contact plate, the other from the slip ring around the steering column. When these two connect, the horn sounds. You just have to connect both these spades to the two terminals on your actual horn button.
I needed to make an additional wire up as well as I only had one that came with my wheel:
Now the last thing you need to do ia actually wire up that horn contact plate properly. The connector that that long pin pushes into is not actually populated but will be a blank so you need to correct that and wire it up.
Look on the backside and you will see the multiconnector that slips onto all the electrical stalk pins. Just pull this backwards gently and it should slip off fairly easily.
There you go. You can see all the female pins that mate with the male pins.
Unclip its lid which hinges off in one direction. The very long arm you see there is the route that leads to where your horn contact plate pin sits. You need to use a similar connector to wire in the brown+white feed from the original orange horn plug.
Just go back to my horn plug that I made up. Look at that round female connector.
Here you can see it fed into the connector down the longest channel and then the bent at right angles.
The other wire coming off that plug is redundant and can just be neatly parked.
Thats about it. Just pull out that horn contact strip of metal a little. I actually found I had to upturn the lower end as well to make a second contact point to get it to work. Don't forget to plug in your other orange airbag connector with the resistor.
Fit the steering wheel, tighten the lock nut and reconnect the battery.