I will try to accurately describe the steps I took in order to make my turn signals and horn work with my Version 3 STi steering wheel. The mods listed here are not extremely difficult, but it is pretty involved. With that said here comes the fun stuff!
STEP 1: Remove airbag and steering wheel.
First disconnect the positive(+) and negative(-) cables from your battery. Wait about five minutes and then pump your brakes to drain the system of any charge. There are two torx screws, size T-30 that holds your airbag to the steering wheel. Here is a good writeup on removing the steering wheel.
Steering Wheel Removal-Scoobymods.com
STEP 2: Remove Clock Spring/Roll Connector.
I do not have any pictures of this procedure, but it isn't hard to understand. First remove the 3 screws holding the steering column covers on. They are located on the bottom of your steering column. Then pull the bottom cover off. Next, remove the 3 screws that hold the clock spring to the column. Then follow the wires under the dash to the connectors. There are two, one looks just like the green and yellow connector behind your airbag and it is a bigger pain in the but to remove because you have to be laying in your floorboard to see it! Disconnect the two connectors and carefully slide them out from under the column. You will have to cut one zip tie and open up a clamp that holds the wires to the column.
STEP 3: Call or PM your favorite Subaru JDM parts importer!
I contacted Jason at Garage Tuning to see if they had a steering column from an Impreza that had been equipped with a Nardi wheel. He did and I purchased the entire column because I didn't know what I would need. I didn't even know if any of this would work, but I figured it would be worth a try. All you really need is the turn signal and headlight stem assembly. It looks like this.
After a couple of days studying my steering column and the assembly I removed from the JDM column, I realized that I might be able to use the center ring from the JDM column to cancel my turn signals. This ring has three small pegs that correspond with three holes on the back of the Nardi wheel and two ridges that cancel the signals.
STEP 4: Remove plastic ring from JDM signal assembly.
This is very easy. Pull the white piece away from the ring and simply pull the ring off the assembly.
Luckily this piece fits perfectly on the stock RS column. The problem is the ridge on the back of the ring needs to be removed. When you turn your signals on there is a small plastic piece that sticks out inside the steering column. This is the piece that needs to be contacted by the two bumps on the ring in order to cancel the signals. With the ring in place the plastic piece will not come all the way out because it hits the ridge on the back of the ring. (Did that make any sense?) So I got out my dremel and cut it off!!
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STEP 5: Cut off ridge on back of plastic ring.
Pretty easy and self-explanatory. This is what you should end up with.
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Ok, the turn signals are not quite finished. The ring sits to far back and doesn’t contact the steering wheel. I have figured out a fix, I am just waiting on a part.