Hi

We suspect that AC in my wife's S90 developed a small leak. She (my wife)started complaining about AC back in April. In May I added one can of R134a. The air was freezing cold again and it lasted almost two months. About a month ago she started complaining again. AC was not completely dead, but produced barely cool air. Also, the AC lines were not "sweaty" as they used to be. This time I bought a two-dial manifold pressure gauge to check freon pressure in the system. I started the car and turned AC to Max. When I connected hoses to the blue gauge (low side pressure), it showed about 25-30 psi and the compressor was ON and did not cycle. I figured it was low on feon again. I connected a can of R134a and started adding freon to the system. The pressure jumped to about 40 psi. I waited 5 more minutes, but the pressure stayed around 40 psi. I thought that the can was empty. While disconnecting the can I heard compressed air was coming out, so it was not completely empty. The compressor was still on and not cycling. I connected another can and the system did not accept much more: it rose to about 45 psi but then dropped back to 40 psi. I waited 5 minutes or more. I could feel that the can was still almost full and not much of freon from the 2nd can entered the system. Finally I diconnected the second can and closed the system. I guess the system accepted enough of new freon because the air in the cabin became much colder and the AC lines in the engine compartment started to sweat again. Given that 40 psi is closer to the correct pressure comparing to 25 psi I had before, I would consider the issue closed for another 2 month if not for one thing: the compressor stays on all the time. Everywhere it says that compressor should cycle on and off. Cycling intervals might vary, but it should cycle on and off. Mine doesn't. It was not that hot yesterday (85F-90F, no direct sun in my garage) and the car was not overheated. Why wasn't my compressor cycling? Is there something wrong? How can I check this? If I did not add enough freon to the system, how can I force it in? What is the correct pressure for my car's AC system (960/S90)?

Raphael