dwags

I own a 2003 Suburban with Quadrasteer and the a/c is acting up. The rear blows nice cold air but the front does not. Here is what happens, For the past 2 years at the beginning of the summer I need to "top off" the 134a charge as there seems to be a very small leak in the system but I think I have found it and made the repair (low side charging valve was leaking). After charging up the system I get great cold air both in the front and the rear after a few days the air out of the front seems to discharge warmer air then the rear. It first gets noticeable while sitting (stopped) in traffic but when accelerating it gets cold again but this stops after a few days and the air out of the front only blows warm air but the rear keeps blowing nice cold air. I add more 134a and again the front starts blowing nice cold air just like the rear but again the cycle starts all over again and within a few days the front gets warm and the rear stays cold!

I have verified that there is not a separate compressor or system for the rear, both the front and rear are served by the one compressor system under the hood.

Why would the rear stay nice and cold and the front not but after topping off the charge the front gets cold again for a few days?