my a/c blows cold for a few min. but will blow hot when idling for more than a minute and the engine temp guage goes to hot. as soon as i get on the hwy the guage returns to normal and air is cold again. is this an a/c clutch problem and if so i've found info on this site on how to set the air gap but it was for a 00 sdd. is it the same for an 08?

 

ya it sounds like you have a problem with the distributer cap over the ac valves, its a big repair...

 

Sounds like you're not getting air flow through your AC condenser and radiator. Maybe the clutch for your radiator fan is worn out?

 

ya it seems kinda like your not getting air flow through you ac condensor and radiator... i think your clutch for your radiator fan is out, simple to replace