I have a 06 PT convertible with 46k. It has an intermittent issue with air not coming out of any of the vents properly. It will do this on heat or AC. It acts as if the fan is in low speed when it is on high. You can here the air pressure from the blower motor when you have it in high. After several minutes or after you have turned the car off, it works normally again but soon returns after about 15 minutes of driving. I had my dealer charge the AC, they said it was low and they thought the core was freezing up. Could this be a blend door and if so which one.