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A/C Pressure Zone "D" Diagnosis

WARNING: This page is about a different car, the 2002 GMC Savana Special, 2002 GMC Savana Camper Special, 2002 GMC Savana, and 2002 Chevrolet Chevy Express. However, it is still accessible from the selected car via links, so may be relevant.
WARNING: Avoid contact with moving parts and hot surfaces while working around a running engine in order to prevent physical injury.
NOTE: For circuit reference, see CONNECTOR IDENTIFICATION  and/or WIRING DIAGRAMS  .
NOTE: Tools Required: ACR 2000 Air Conditioning Service center (J-43600).
NOTE: Definition: The low side pressure is lower than normal and the high side pressure is higher than normal.
  1. Were you sent here from the A/C PERFORMANCE TEST ? If so, go to next step. If not, go to A/C PERFORMANCE TEST  under PERFORMANCE TESTS.
  2. Feel the liquid line before the orifice tube. Is the liquid line cold before the orifice tube? If so, go to next step. If not, go to step  8.
  3. Feel along the surfaces of the following high side components for a sudden drop in temperature. The high side components should feel warm/hot from the compressor all the way to the orifice tube:
    • The Compressor Discharge Hose
    • The Condenser
    • The Liquid Line Between The Condenser And The Orifice Tube
    Is there an abrupt drop in temperature noted along the surfaces of any of the listed components? If so, go to step  7. If not, go to next step.
  4. Feel the liquid line at the orifice tube location for extreme cold, possibly accompanied by heavy frost. Feel along the liquid line after the orifice tube location for warm temperature. Is the liquid line extremely cold at the orifice tube location and warm after the orifice tube location? If so, go to step  11. If not, go to next step.
  5. Feel along the surfaces of the following low side components for a sudden change in temperature:
    • The Evaporator Inlet Tube Between The Orifice Tube And The Evaporator Core
    • The Evaporator Outlet Tube Between The Evaporator Core And The Compressor
    • The Accumulator
    • The Compressor Suction Hose
    Is there an abrupt temperature change felt along the surfaces of any of the listed components? If so, go to step  7. If not, go to next step.
  6. Feel along the surfaces of the following low and high side components to compare the overall temperatures:
    • The Evaporator Inlet Tube Between The Orifice Tube And The Evaporator Core
    • The Evaporator Outlet Tube And The Compressor
    • The Compressor Suction Hose
    • The Compressor Discharge Hose
    • The Condenser
    • The Evaporator Inlet Tube Between The Condenser And The Orifice Tube
    Are the overall temperatures of the low and high side components close to the same, both only mildly warm? If so, go to step  14. If not, go to step  8.
  7. Recover the refrigerant. See RECOVERY, EVACUATING & RECHARGING in GENERAL SERVICING PROCEDURES article in GENERAL SERVICING. Remove the restriction from the component, or replace the component which produced an abrupt temperature drop. After repairs are complete, go to step  9.
  8. Recover the refrigerant and evacuate the system. See RECOVERY, EVACUATING & RECHARGING in GENERAL SERVICING PROCEDURES article in GENERAL SERVICING. Record the weight of the recovered refrigerant. Is the weight of the recovered refrigerant charge equal to or above the system capacity? See SPECIFICATIONS . If so, go to step  10. If not, go to step  10.
  9. Recharge the A/C system. See RECOVERY, EVACUATING & RECHARGING in GENERAL SERVICING PROCEDURES article in GENERAL SERVICING. Is the cooling performance improved? If so, go to step  21. If not, go to next step.
  10. Leak test the system. See LEAK TESTING in GENERAL SERVICING PROCEDURES article in GENERAL SERVICING. Repair any leaks. After repairs are complete, go to next step.
  11. The orifice tube is restricted. Replace the orifice tube. See ORIFICE TUBE  under REMOVAL & INSTALLATION. If the orifice tube was restricted, note the type of debris present. Are there metal flakes present? If so, go to next step. If not, go to step  13.
  12. Remove the compressor hose assembly from the vehicle. See COMPRESSOR HOSE  under REMOVAL & INSTALLATION. Inspect the hose/line for debris by blowing shop air through one end of the hose while covering the other end with a shop towel. Note the amount of debris collected in the shop towel. Is there a large amount of debris collected in the shop towel? If so, go to step  18. If not, go to step  20.
  13. If the orifice tube was restricted with a brown/black residue, perform the following: Flush the A/C system. See FLUSHING PROCEDURES in GENERAL SERVICING PROCEDURES article in GENERAL SERVICING. Replace the accumulator. See ACCUMULATOR  under REMOVAL & INSTALLATION. After repairs are complete, go to step  21.
  14. Recover the refrigerant. See RECOVERY, EVACUATING & RECHARGING in GENERAL SERVICING PROCEDURES article in GENERAL SERVICING. Disconnect the compressor hose from the compressor. Inspect for the presence of debris in the compressor suction port. Is there debris present in the compressor suction port? If so, go to next step. If not, go to step  19.
  15. Remove the debris from the suction port. Inspect the orifice tube for damage or debris. See ORIFICE TUBE  under REMOVAL & INSTALLATION. Is there evidence of damage or debris? If so, go to step  17. If not, go to next step.
  16. If the orifice tube does not show any signs of damage or debris, remove the compressor hose assembly from the vehicle. See COMPRESSOR HOSE  under REMOVAL & INSTALLATION. Inspect the hose/line for debris by blowing shop air through one end of the hose while covering the other end with a shop towel. Note the amount of debris collected in the shop towel. Is there a large amount of debris collected in the shop towel? If so, go to step  18. If not, go to step  19.
  17. Replace the orifice tube. See ORIFICE TUBE  under REMOVAL & INSTALLATION. If the orifice tube was restricted, note the type of debris present. Are there metal flakes present? If so, go to step  12. If not, go to step  13.
  18. If there was a large amount of debris collected in the shop towel from the compressor hose assembly, replace the accumulator. See ACCUMULATOR  under REMOVAL & INSTALLATION. Install an A/C refrigerant filter. See REFRIGERANT FILTER  under REMOVAL & INSTALLATION. Install a suction screen. See REFRIGERANT SUCTION SCREEN  under REMOVAL & INSTALLATION. After repairs are complete, go to next step.
  19. Install the compressor hose assembly. See COMPRESSOR HOSE  under REMOVAL & INSTALLATION. After repairs are complete, go to step  21.
  20. Install the compressor hose assembly. Install an A/C refrigerant filter. See REFRIGERANT FILTER  under REMOVAL & INSTALLATION. Recharge the A/C system. See RECOVERY, EVACUATING & RECHARGING in GENERAL SERVICING PROCEDURES article in GENERAL SERVICING. After repairs are complete, go to next step.
  21. Record the low and high side pressures and the I/P outlet air temperature after repairs are performed. Compare the pressures and outlet temperature to those listed in the A/C Performance Chart. See A/C SYSTEM PERFORMANCE SPECIFICATIONS - WITH FRONT A/C  or A/C SYSTEM PERFORMANCE SPECIFICATIONS - WITH REAR A/C  tables. Are the readings within the specified ranges? If so, go to next step. If not, go to A/C PERFORMANCE TEST .
  22. Operate the system in order to verify the repair. Did you correct the condition? If so, system is okay. If not, go to step  2.
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