Insufficient information, please ask the question
in a sensible clear way.
No, you use the ohms position.
If you are talking about checking to see if the charge is right, yes it must be running.
No, the circuit should not be energized when checking the resistance of a circuit.
Try checking the low pressure switch.
The way that you know if your ac in your vehicle needs to be charged is by checking the psi level on the ac system. You check the level with a gauge throught the low side port on your ac system. There is a great web site www.idqusa.com that has alot of helpfull information about your ac system.
Start out by checking the a/c blower and the blower resister.......
try checking main fuse box located in top of dashboard release clip located just above where the ac switch is (or would be if the vehicle doesnt have ac fitted)
First thing check to see if you have any freon in the system and if so start checking the electrical for the blowers.....
Start out by checking the freon levels and if that is okay then check the pressure switches and the wire harness to the clutch....
I would start by checking the fuse, the relay, and the connector on the blower itself.
Start out by checking the blower motor resister......
Is the rear blower functioning? If so the AC system may be undercharged. I would first suggest checking that the system is properly charged, if it is then there may be a blockage of some type in one of the lines.