An air conditioning system cannot "blow hot air". Because physics. The pressure differential can cause a drop in temp, or no drop it temp. It cannot RAISE the temp.
When the system is switched to ON, with the engine running of course, there should be after about one second or so, an increase in the refrigerant pressure sensor value from static, and it should continue to rise until the cooling fans come on, then it may level off depending on how hot it is.
If there is not enough pressure to turn the fans on, and the system is known to be FULL BY WEIGHT (which, you cannot tell with a static gauge reading, full by weight means the system was evacuated, vacuum placed and held, and recharged the full amount as the label under the hood states), then chances are the RCV is bad. However in some cases, the compressor is the culprit. And, also, the pressure sensor itself can have issues although that was usually more problematic on the older (BRM era) cars than on the CR era cars.
