Today measured pressures for kicks' from my xjr. Outside temp was 21'c, engine hot and running and engine bay warm, hvac on but ac off, requested 21'c for the temperature.
As enginebay was warm after a drive, pressure was a bit rised as being 7bar. As I turned ac on, low pressure dropped almost instantly to 3bar and after few seconds to 2.5bar. Same time high side raised to the 17bar and somewhere after 15bar fan half speed turned on. Then I held engine against it's 3000 rpm limiter just to see that low pressure side went to 1.5bar and high side raised and stayed at 22bar. Fan was then at full speed. After revving pressures reveted back to the idle state and fan speed back to half.