Getting the Horn to Work

Getting the horn button to work requires some modifications. In a nutshell, this is how the horn button works on an '02. On the steering column, a thin sheetmetal brass ring (technically called a slip ring) is electrically connected to the coil of the horn relay. On the steering wheel, a small spring-loaded carbon (or brass) plunger is connected to the horn button. If everything works correctly, the spring plunger is always in contact with the brass ring as you turn the steering wheel. When you push the horn button, the circuit is closed to the relay and the horn goes off.

On a 320i, the mechanical hardware for the horn button is reversed. The plunger is on the steering column, and the brass ring is on the steering wheel. Don't ask me why the BMW engineers did it this way. They just did.

Detail of what's behind the scenes.

You have two options. One: Take a sharp utility knife, and make a radial cut completely through the brass ring on the 320i steering wheel. Once the ring is split, use pliers to carefully bend up one end of the ring high enough to form a cantilever leaf spring. Then bend the tip of the ring over to form a smooth contact surface for the steering column.

This method works well with the standard 4-spoke 320i steering wheel because there is little, if any, access to the internal wires going to the horn buttons. It can be used for the 320is steering wheel, too.

Two (for the 320is steering wheel): Remove the brass ring. Carefully enlarge one of the three holes on the base of the steering wheel hub just large enough to press fit the spring plunger into it. (Note: For the particular plunger I had, a 17/64-inch diameter hole was needed). Surprisingly, the location of the hole pattern is almost on the center of the slip ring on the steering column. Before you install the plunger into the 320is steering wheel, you may need to lengthen the wire.