08 F350 AC problem / delay start

[RobertRTG]

I live in Pheonix Arizona so let me start by saying the AC is absolutely the most important part of the truck.

I have an 08 6.4L F350 and it takes about 15 minutes of driving before the AC will start blowing cold air. Everything else works fine but when the AC is on it blows warm air for the first 15 minutes of driving. Then after 15 minutes it blows cold air. I have tried pushing all of the buttons and lowing or raising the temp setting but nothing will get the AC to blow cold air until it has been driven for 15 minutes.

Also this only happens on the first start. When I start the truck in the morning it blows warm air for 15 and then starts blowing cold. If I park the truck for lunch and then get back in the AC works right away.

Can anybody tell me what is going on here? I hate the idea of taking it in for service without knowing the problem ahead of time.

Thank you
Robert

2008 F350 6.4L Diesel Lariat crew cab 4x4