I have a clicking noise that comes and goes. It is coming from somewhere in the front dashboard. I have been able to determine that it is associated with the AC because when I shut off the AC the noise goes away. As soon as I turn it back on the noise starts again. Sounds like a ticking sound of a clock. Any help would surely be appreciated. My vehicle is a 2003 Yukon XL
Thanks,

Do you have the automatic A/C controls? Does it change or stop if you change the air flow from dash to floor?

There are motorized damper operators that vary the air flow into the ducts. On our Tahoe, one of these gets "stuck" and hunts back and forth making a "scrunch, scrunch" or racheting (socket-wrench) sound over and over. This particular one is on the driver side floor duct under the dash... almost right above where your right knee would be. When you're driving it sounds like it's coming from the instrument cluster, but if you stick your head down there you can tell where it is coming from.

The actuators were probably junk when new. Credit GM for sourcing the cheapest parts. I've already replaced one for the rear a/c but haven't done the front. I think the rear a/c one was around $80 for the part.