Its nearly impossible to see when the clutch is engaged when charging the ac in my 2015 SRX. I heard to get an accurate reading the clutch has to be engaged.

The only way I can tell if my clutch might be engaged is the cooling fan goes on when the clutch is engaged. Is this correct? I notice on my ac low pressure gauge gage drops in PSI when the fan is engaged. So my other question would be should I be reading the PSI level when the cooling fan is engaged?