Auto Air Conditioning & Heater Repair: 97 Ford E450, infrared thermometer, air doors

Question
I have a 97 Ford E450 with a coach bus body the a/c for the cab also runs the rear a/c the cab a/c won't blow cold but the rear unit works good. the low side pressure is on the high side 40-50 psi. I have checked all air doors for proper operation  I checked the orifice tube system has been evacuatedand recharged still the same Idid notice the tube into the evaperator is cold but coming out it is warm what am I missing Thanks Warren

Answer
Warren,

It sounds like you might have an internal restriction with the evaporator core because the line coming out of the evaporator should be a little warmer than going in but not warm. To check the evap. core you will have to gain access to the evap. core and use a infrared thermometer and just go across the evap. and you should find the temperature change and theres your internal restriction.