2001 Mercury Marquis

I have a 2001 Mercury Grand Marquis. It is a 4.6 liter motor, and has 116000 miles on it. It has the police interceptor package on it. Up until now it has been a GREAT car. Recently though, I have had some problems with my ac system. It has the automatic cooling system, where you just press AUTO and adjust speed and cooling of ac. Whether the day is 100 degrees or 20 degrees the system will freeze up. You can hear that the blower is on, but very little air comes out of the vents. What does come out is freezing cold. I cant adjust where it comes out, floor, vent, defrost. I took it to 2 ac mechanics, they say that the system had to much pressure, so they released some. Then they replaced the high and low pressure sensors on the ac system. Still the same thing is happening. It's about to get very hot here and I would really apreciate some help from you knowlegeable fellas. THANKS
February 26, 2007.

On fords with temp control, there are 2 important sensors, most important is the cabin mounted sensor that actually control the temp control system, it's usually mounted above the clove box behind the dash, the other is external and is the ambient temp sensor. The other possibility is the pressure cycling switch mounted on the low side of the system is stuck! You can usually tell that if the ac compressor never cycles off and on, just always running.

Mar 4, 2007.
Something else that I forgot to mention is that my ac compressor is also whining, will that make a difference? Thanks for your help

Mar 4, 2007.