I have a 2002 dodge ram 1500 4x4 5.9liter. The prboblem with my a/c is that when I turn the fan switch to full high or any speed in fact. It cont to blow as if it is stuck on low. It does this either on cold or hot. If I move the switch to defrost or the floor it works just fine. So basically it does not blow out at a high speed regardless what it is on. I have no idea as to what I need to check