I checked and filled my system last week and found that if the AC is off, the pressure on the low side was real high. (Like 60+) When the AC is on, the compressor runs and there is a big difference between the low and high sides. Normal for AC on was like 25-30 on my guage once I had enough fluid in.
When my fluid was low the compressor clutch would not stay engaged and the idle would surge by 200 rpm each time it disengaged. The low side pressure was < 15.
