GM Service Manual Online
For 1990-2009 cars only

Step

Action

Yes

No

DEFINITION: The low side pressure is higher than normal and the high side pressure is lower than normal.

    • Malfunctioning Air Conditioning (A/C) Compressor
    • Refrigerant Under Charge

1

Were you sent here from the air conditioning (A/C) System Performance Test?

Go to Step 2

Go to Air Conditioning (A/C) System Performance Test

2

After continued operation of the A/C system, do the low and the high side pressures equalize or become static?

Go to Step 5

Go to Step 3

3

  1. Refer to the pressures recorded during the A/C System Performance Test.
  2. Inspect for the following conditions:
  3. Caution: Refer to Moving Parts and Hot Surfaces Caution in the Preface section.

    • The low side pressure is equal to or greater than the specified pressure range of the A/C Performance Table. Refer to Air Conditioning (A/C) System Performance Test .
    • The high side pressure is less than the specified pressure range of the A/C Performance Table. Refer to Air Conditioning (A/C) System Performance Test .
    • The low side refrigerant line at the compressor feels cool to warm.
    • The high side refrigerant line at the compressor feels warm to hot.

Do the listed conditions exist?

Go to Step 5

Go to Step 4

4

  1. Refer to the pressures recorded during the A/C System Performance Test.
  2. Inspect for the following conditions:
  3. Caution: Refer to Moving Parts and Hot Surfaces Caution in the Preface section.

    • The low side pressure is greater than the specified pressure range of the A/C Performance Table. Refer to Air Conditioning (A/C) System Performance Test .
    • The high side pressure is less than the specified pressure range of the A/C Performance Table. Refer to Air Conditioning (A/C) System Performance Test .
    • The low side refrigerant line at the compressor feels warm.
    • The high side refrigerant line at the compressor feels warm to hot.

Do the listed conditions exist?

Go to Step 5

Go to Air Conditioning (A/C) System Performance Test

5

The A/C system has a low refrigerant charge.

Evacuate and recharge the A/C system. Refer to Refrigerant Recovery and Recharging .

Is the action complete?

Go to Step 6

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6

  1. After you perform the repairs, record the following:
  2. • The low and the high side pressures
    • The instrument panel outlet air temperature
  3. Compare the pressures and the temperature to those listed in the A/C Performance Chart. Refer to Air Conditioning (A/C) System Performance Test .

Are the readings within the specified ranges found on the A/C Performance Chart?

Go to Step 13

Go to Step 7

7

The A/C compressor is malfunctioning.

Remove the thermal expansion valve (TXV) and inspect for contamination. Refer to Thermal Expansion Valve Replacement .

Did you find metal flakes on the TXV?

Go to Step 9

Go to Step 8

8

Inspect the TXV for a brown, powdery residue indicating desiccant in the A/C system.

Is a brown, powdery residue present?

Go to Step 11

Go to Step 12

9

  1. Remove the compressor hose from the compressor. Refer to Compressor Hose Assembly Replacement .
  2. Inspect for metal flake contamination at the line connections and the compressor ports.

Is metal flake contamination present?

Go to Step 10

Go to Step 12

10

  1. Replace the A/C compressor. Refer to Air Conditioning Compressor Replacement .
  2. Replace the TXV. Refer to Thermal Expansion Valve Replacement .
  3. Evacuate and recharge the A/C system. Refer to Refrigerant Recovery and Recharging .

Is the action complete?

Go to Step 13

--

11

  1. Replace the TXV. Refer to Thermal Expansion Valve Replacement .
  2. Replace the A/C compressor. Refer to Air Conditioning Compressor Replacement .
  3. Replace the receiver dehydrator. Refer to Receiver Dehydrator Replacement .
  4. Evacuate and recharge the A/C system. Refer to Refrigerant Recovery and Recharging .

Is the action complete?

Go to Step 13

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12

  1. Replace the A/C compressor. Refer to Air Conditioning Compressor Replacement .
  2. Evacuate and recharge the A/C system. Refer to Refrigerant Recovery and Recharging .

Is the action complete?

Go to Step 13

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13

Operate the system in order to verify the repair

Did you find and correct the condition?

System OK

Go to Symptoms - HVAC Systems - Automatic