Z3 air/heat selector knob broken

[mgibso19]

2001 Z3 3.0i Roadster
Has anybody had any experience with the temperature selection knob above the gearshift breaking? I had the BMW dealership repair it about a year ago and they replaced the front knobs. The problem showed up again in a few months but the car was out of warranty. Everything else works like the fan switch and vent selector.

Before I tear into the console, I'd like to know if the problem is simply the knob, or is there a cable that has broken inside the dash.

Also, has anybody replaced the shocks on their car yet? We have over 80,000 miles on the car and it's getting a little bumpy to drive....

Thanks in advance to anyone who has information....Mark