I have an 02' Tremor with a 3.0 flex fuel. Since the beginning of the summer I started to have ac issues (this isn't a daily driver so that's why I haven't asked earlier). Some reason when I first turn air conditioning on it just blows hot air and then after about 15 minutes on full blast it starts working and blows nice and cold. If i get in within 30 minutes of turning the truck off it still works. Any explanations?