Do I check the refrigerant pressure with the car running, and the ac on?

Or do I need to jump the leads of the pressure switch first and then check the refrigerant pressure with the car running and the ac on?

I know that if the refrigerant pressure is low the compressor won't engage, and if the pressure switch is bad the compressor won't engage either.

I am thinking that if the refrigerant pressure is good, it is probably going to be a bad switch.

Going to have someone check the pressure with a gauge tomorrow.