We love our new 2010 Sonata. But whenever we turn on the heater or the ac, clicking noises come from behind the dashboard, both sides, for a minute or less. I tested by switching back and forth between ac and heating; each time I switch, the clicking starts. It also clicks a lot more with road bumps. I suspect the tubes in the heating / cooling system are expanding and contracting. Any one else ever notice this odd problem?