2005 Elantra GL, Manual Transmission -

While Sitting, the A/C blows out pretty cold. Start driving and the A/C starts getting rather warm. After driving for a while, A/C is blowing out HOT. The lines are nice and cool. I'm thinking it's the compressor but I could be wrong. In the past, I've heard the belt chirping when the compressor first kicks on. I never got around to replacing the belt though (or at least tightening it for that matter.) I'm guessing the looseness finally caused the compressor to go? Any thoughts?

 

Brought it to the shop. The mechanic told me it's the thermostat (?) Could he mean the sensing bulb??