Nope. The orifice that starts the cooling process is under the hood. There isn't much point to doing the cooling there, so that insulation is there to keep the liquid refrigerant cold so it won't start to vaporize until it gets in the evaporator in the dash.
If the system isn't cooling sufficiently, it may just be low on charge. On GM vehicles, the only way to know is to recover what is in there now, then pump in the measured amount called for in your system. If the system is low, you may see frost forming on the hose under the hood that leads from the condenser to the accumulator by the firewall. Frost or ice will form where the liquid is turning to a vapor, and that is supposed to occur in the dash. If the charge is low, it will occur sooner, meaning under the hood.
Another common problem on some GM models is a plugged orifice tube. You didn't list the model you have, and I can't find anything with a 7.0L engine, so I can't look up the AC system you have. If that tube is plugged, the cooling will take place at the hose connection where that tube is inserted, under the hood. What little refrigerant does get through won't do an effective job in the dash.
Monday, June 15th, 2015 AT 6:48 PM