2003 Expedition with front and rear (dual) systems. Doesn't seem to cool as fast as it used to. Bought a do-it-yourself can with a gauge. Based on a near 90F temperature, the can said the pressure should be 45 psi. It was well over that, think about 60 psi. I turned off the a/c compressor and it went over 80 psi. I didn't add any freon, disconnected the gauge and hopped on-line to see if there's a different pressure range for dual systems. The only thing I was able to find was this page with a comment saying a dual system should be between 60 and 70 psi.

how do you recharge the a/c on 2003 expedition - JustAnswer

Answers, comments, suggestions greatly appreciated.