What year is your titan? My 04 Titan has done the same thing. Basically on mine the "guts" on the inside of the fan speed switch stripped out...I havent found where you can replace just the switch, you have to replace the whole unit. I found some threads about it a few weeks ago. Mine went out last year while at the OBX fishing....couldnt get the ac to blow at any speed and roasted the whole trip home. Made for a long ride home !
Yeah mine is a 04 CC and yeah I was looking at it last night and its the interior switch that is stripped and I don't think I can do the switch fix I found on here so going to hunt ebay and junk yards for a new unit I guess