AC Testing...back AC ON?

[Rob Adams]

Was hoping I could get some clarification on this. I have the rear AC on my 05 expedition and when I'm testing the high/low side with the AC on max/full, should the rear be on full as well? I'm noticing 2 different pressure readings when the rear is off vs on. I'm having issues with the AC taking forever to cool down when the temps are above 90 degs and am trying to figure out where my issue is. Wanted to start with just getting good solid readings.

 

[riphip]

Yes, have everything running. Is 1 single system with ability to not circulate rear system unless needed. To test pressures, etc, front and rear must be operating.
If possible, use a HD shop fan in front of the grill blowing towards the condenser to imitate air flow driving on the street.