I set out to understand how it should work. When a signal is activated, a small plastic rectangle is pushed toward the center of the steering column. This rectangle is in the same plane as a notched plastic disk which rides on the column. The steering wheel engages this disk with a slotted sleeve. On my car, this sleeve was plastic and it was broken.
Checking on ebay, I found other steering wheels with a cast aluminum sleeve, but these had airbags and/or radio controls on them as well. So I designed a replacement to be machined from steel or aluminum.
The lowest price I was quoted was $30, which is not unreasonable for the time involved, despite the simple design. But for that price I could buy a used steering wheel if I was willing to wait for shipping. Instead, I decided to make one myself from steel sheet.
Here it is mounted on the steering wheel. It is not pretty but it works.
