A/C Question, Trailblazer 4.2

I'm gonna be charging up my system this weekend and was wanting to know if I had to have the rear A/C turned on as well as the front during this procedure?

Depends on HOW you're charging the system.

Are you just blowing a pounder can of refrigerant into the system because there's a slow leak you haven't bothered to fix?

Has the system been opened to fix a leak, vacuumed, and you're adding the "sticker capacity" of refrigerant?

Are you adding refrigerant based on duct temperature readings (i.e., adding until the duct temperature stops dropping, and then 1/4 lb. additional.)

Depends on HOW you're charging the system.

Are you just blowing a pounder can of refrigerant into the system because there's a slow leak you haven't bothered to fix?

Has the system been opened to fix a leak, vacuumed, and you're adding the "sticker capacity" of refrigerant?

Are you adding refrigerant based on duct temperature readings (i.e., adding until the duct temperature stops dropping, and then 1/4 lb. additional.)

I had the system evacuated so I could replace the compressor

I had the system evacuated so I could replace the compressor
Did you replace ALL the O-rings to prevent future leaks while the system was empty?

Did you have the system vacuumed AFTER the compressor was replaced?

Did you replace ALL the O-rings to prevent future leaks while the system was empty?

Did you have the system vacuumed AFTER the compressor was replaced?

There wasn't any leaks, the compressor went bad and I replaced it and the orifice tube. I just want to know if I need the back AC on or not while charging it.

There wasn't any leaks, the compressor went bad and I replaced it and the orifice tube. I just want to know if I need the back AC on or not while charging it.
Was the system vacuumed AFTER the compressor was installed?

Was the system vacuumed AFTER the compressor was installed?

Yes, can you answer my question now?

I can't answer your question until you answer all of mine.

Are you charging by weight, using the "sticker capacity" or are you charging based on duct temperature?

Simple yes or no, thanks for your help

It's a valid (and important) question. If charging by refrigerant weight, you may not even need to have the vehicle running (depending upon temperatures). If charging by system performance, both halves of the system should be operating. Been there - I have two Chevy vans with dual air, and one has lost belly seals on the compressor once already.

Hopefully the proper volume of oil has already been added to the system as well as the compressor - That question has not come up yet.