I have a 2004 GMC Sierra Z71 with a 5.3. The ac doesn't get very cold and if I get on it it starts blowing warm then when u get to speed it starts cooling off again. Also if your sitting and idling it warms up again. I was thinking about changing the accumulator and orifice tube and vac it down and recharge it. But my friend told me he had that problem with a newer nissan xterra and it ended up bein a thermatic switch. Does anyone know what the problem could be? Thanks for your help!