GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Pontiac 🢒 2000 🢒 Firebird 🢒 HVAC 🢒 Heating, Ventilation and Air Conditioning 🢒 Cooling Insufficient - Air Conditioning (A/C) System - Pressure Zone A

A/C System Pressure - Zone Classification Graph
Object Number: 590674 Size: MF

Step

Action

Value(s)

Yes

No

1

Were you sent here from the Cooling Insufficient, A/C System diagnostic table?

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Go to Step 2

Go to Cooling Insufficient - Air Conditioning (A/C) System

2

During continued operation of the A/C system, does the compressor clutch disengage and re-engage with no abnormal change to the low and high side pressure readings?

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Go to Step 3

Go to Step 4

3
  1. Check for an intermittent in the clutch coil and/or the clutch coil circuit. Refer to HVAC Compressor Clutch Does Not Engage in HVAC Systems - Manual.
  2. If replacement of the clutch coil is necessary, recover the refrigerant.
  3. Replace the clutch coil and/or repair the clutch coil circuit.

    4. For clutch coil replacement, refer to Compressor Clutch Coil Removal (V5 - Conventional Mount) and Compressor Clutch Coil Install (V5 - Conventional Mount) or Compressor Clutch Coil Removal (V7 - Direct Mount) and Compressor Clutch Coil Install (V7 - Direct Mount) .

Is the repair complete?

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Go to Step 12

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4

Did the customer concern mention that the A/C system output temperatures are good at first, but then turn warm during extended drives?

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Go to Step 5

Go to Step 7

5

The engine still running with a speed of 2000 RPM.

During extended operation of the A/C system, does the low side (and possibly the high side) pressure increase significantly (possibly accompanied by heavy frost on the liquid line between the orifice and the evaporator)?

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Go to Cooling Insufficient - Air Conditioning (A/C) System - Pressure Zone B

Go to Step 6

6

Take the vehicle on a test drive under the same conditions as the customer, to verify the concern.

Has the concern been verified?

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Go to Cooling Insufficient - Air Conditioning (A/C) System - Pressure Zone B

Go to Step 11

7

Compare the low and high side pressures to those listed in the A/C performance table. Refer to Cooling Insufficient - Air Conditioning (A/C) System .

Is the high side pressure slightly above normal pressure?

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Go to Step 8

Go to Step 9

8
  1. The refrigerant system oil charge level may be too high.
  2. Evacuate the refrigerant system.
  3. Check the amount of refrigerant oil removed from the system.
  4. Charge the refrigerant system to specifications, using care to maintain the proper oil level.
  5. Leak test the refrigerant system. Refer to Leak Testing .

Are the operations completed?

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Go to Step 10

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9
  1. The refrigerant system may contain too much moisture.
  2. Evacuate the refrigerant system.
  3. Charge the refrigerant system to specifications.
  4. Leak test the refrigerant system.

    5. Refer to Leak Testing .

  5. If no leaks are found, replace the accumulator. Refer to Air Conditioning Accumulator Replacement .

Are the operations completed?

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Go to Step 10

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10

Compare the outlet temperature to those listed in the A/C performance table. Refer to Cooling Insufficient - Air Conditioning (A/C) System .

Is the outlet temperature within specifications?

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Go to Diagnostic System Check in HVAC Systems - Manual

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11
  1. Start the engine and allow the engine to idle.
  2. With an accurate thermometer still installed to the IP center air outlet.
  3. Set the HVAC control to the following positions:
    4. • The A/C on
    • The temperature control to coldest position
    • The mode control knob to UPPER (IP outlets)
    • The blower switch to high
  4. Elevate and maintain the engine speed at 2000 RPM.
  5. Allow the low and high side pressure readings to stabilize, if necessary.

    6. (Stabilization usually requires 2-3 minutes.)

  6. Record the low and high pressure readings and the delivered air output temperature.
  7. Compare the low and high side pressures and the output temperatures to those listed in the A/C Performance Table.

    8. Refer to Cooling Insufficient - Air Conditioning (A/C) System .

Are both the low and high side pressures as well as the output temperatures within specifications?

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System OK

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12
  1. Evacuate and charge the refrigerant system.
  2. Leak test the refrigerant system.

    3. Refer to Leak Testing .

Are the operations completed?

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Go to Step 13

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13
  1. Start the engine and allow the engine to idle.
  2. With an accurate thermometer still installed to the IP center air outlet.
  3. Set the HVAC control to the following positions:
    4. • A/C button to ON
    • Temperature control to full cold
    • Mode control knob to UPPER (IP outlets)
    • Blower switch to high
  4. Elevate and maintain the engine speed at 2000 RPM.
  5. Allow the low and high side pressure readings to stabilize, if necessary.

    6. (Stabilization usually requires 2-3 minutes.)

  6. Record the low and high pressure readings and the delivered air output temperature.
  7. Compare the low and high side pressures and the output temperatures to those listed in the A/C Performance Table. Refer to Cooling Insufficient - Air Conditioning (A/C) System .

Are both the low and high side pressures as well as the output temperatures within specifications?

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Go to Diagnostic System Check in HVAC Systems - Manual

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