The clockspring recall does not involve model year 1999. Although the horn circuit uses clockspring wires, the symptoms described by RMcNee don't sound like the clockspring to me.
Since the problem reveals itself at one extreme of the wheel tilt, I think removing the steering column shroud and wiggling wires will find a loose connector or broken wire. I'm betting on the connector being pulled as the wheel is tilted - to the point of losing electrical contact.