Any A/C experts? aka very knowledgeable

ok, i hope someone responds to this thread.  We did a sheetmetal ac box with all the factory GM ac parts, compressors, new drier, condensor, new blower motor fan, but heres the catch.  We couldnt use the factory evap coil because of the size, so we used a 98 honda civic evap coil with an expansion valve.  the factory GM evap coil used an orfice tube.  the evap coil has a brand new expansion valve, clean filter, etc.  But however its not cooling as cold as it should? is it because its not releasing ENOUGH freon or too little? i know mixing the parts has something to do with it, but i know there is a way to get around it.  domestic & import.

Edited: 4/7/2010 4:18:09 PM by BagD72Chevy

I'll talk basics first, then discuss possible issues. In the expansion valve A/C system, the freon is passed through a drier which removes moisture from the refrigerant to maximize the efficiency of the refrigerant. No phase change occurs as the refrigerant passes through the drier. From there, the refrigerant is then passed through the expansion valve. Some expansion valves have a sensing line that is attached to the suction of the A/C compressor. The expansion valve senses the pressure at the suction of the A/C compressor and modulates to maintain the pressure at the compressor suction.  In the orifice tube system, the pressure drop across the orifice tube is proportional to the pressure into the orifice tube. So, the orifice tube system maintains the pressure at the suction of the A/C compressor by cycling the compressor on and off via a clutch. Common on GM vehicles. Out of the expansion device we get a low temperature liquid refrigerant. Air from the passenger's compartment passes across one side of the coils in the evaporator. The low temperature liquid refrigerant passes through the other side of the coils. The refrigerant removes heat from the air in the passenger's compartment and returns to the A/C compressor suction as a low temperature gas (phase change).   -Now there may be a few issues here.  Are you checking temp at the vents?  Is so you have about the same cfm as before but less surface area to exchange the heat and pull down the temperature of the air charge inside the vehicle. -Other possibility is that the lower surface area does not promote enough heat transfer to complete the phase change in the evaporator and the compressor suction is seeing some liquid.  -Theoretically the temperature of the evaporator should be the same provided it's not too much smaller or larger, this temperature is the saturation temperature of the working fluid (freon).   Question- Are the components from both systems designed for R134a/R12, whichever you are using?  When you connect the A/C gauges what are the low side and high side pressures?  I don't think intermixing the parts will cause the A/C not to work, but it may not work as well.  However I have a feeling the problem lies in the control system, which relies on it being orifice tube/ expansion valve.  Does your expansion valve have a provision to monitor the compressor suction pressure?   Hope this helps some, post up if you figure it out or have more questions. -Ryan