Performance Test: Notes

If all components such as air doors, blowers, vacuum motor, etc. are functioning properly, the efficiency of the system may be determined by a performance test as outlined below.

1. After purging pressure lines on Charging Station J-8393 (or suitable substitute) connect high pressure line to fitting on high pressure vapor line, and low pressure line to evaporator gauge fitting on suction throttling (POA) valve. Disconnect vacuum hoses from both power servo power units and plug hoses.
   Fig 1: A/C Performance Charts - Cadillac Series 75

   Courtesy of GENERAL MOTORS COMPANY
   Fig 2: A/C Circuit Diagram (Rear Unit) - Cadillac Series 75

   Courtesy of GENERAL MOTORS COMPANY
   Fig 3: A/C Circuit Diagram (Front Unit) - Cadillac Series 75

   Courtesy of GENERAL MOTORS COMPANY
2. Carefully close hood as far as possible and place 24" blade auxiliary fan 30" from front bumper. Direct air stream to center of radiator grille.
3. Open all doors and windows. Place a thermometer in air stream of auxiliary fan. Place another thermometer in right front A/C outlet grille. Thermometer bulbs must not touch any metal.
4. Use a combination humidity indicator and thermometer (Humidicator J-6076) placed on right side of cowl air intake grille so that entering air passes over bulbs and readings may be taken of temperature and humidity of this entering air.
5. Place a thermometer in right rear roof outlet and open deflector doors. Place another thermometer on center of package shelf over return air intake.
6. Turn on auxiliary fan, start engine and run at 2000 RPM. After systems have operated for five minutes carefully record the following data:
   1. Humidity and temperature of air entering air intake grille.
   2. Discharge air temperature at right front A/C outlet.
   3. Temperature of air entering radiator grille.
   4. Compressor head pressure.
   5. Front evaporator pressure.
   6. Discharge air temperature from right rear outlet.
   7. Temperature of air returning to rear evaporator assembly.