1. Verify the proper system charge first. Without auxiliary air the charge specification is 36 oz, with auxiliary air the charge specification is 53 oz. Also verify the system is charged with non-contaminated R-134a.
2. If the system charge is correct, start the engine and let the A/C compressor run. Using a non contact temperature gun or by hand, check for any temperature difference in any of the lines that would indicate a restriction in the system. Once found, check for a restricted line, or excess oil if the restriction is found to be at the accumulator, evaporator, or condenser. Address the restriction as needed and recheck operation.