GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Buick 🢒 2005 🢒 Terraza 🢒 HVAC 🢒 Heating, Ventilation and Air Conditioning 🢒 Air Conditioning (A/C) Diagnostics - Pressure Zone A

Step

Action

Value

Yes

No

DEFINITION: The high and low side pressures may be normal or slightly less than normal.

    • Air Delivery Concern
    • Slight Refrigerant Under Charge
    • Refrigerant Contamination

1

Were you sent here from the A/C System Performance Test?

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Go to Step 2

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

2

Refer to the panel air outlet temperatures recorded during the A/C system performance test.

Does the discharge air temperature between the right and left center panel outlets vary by more than 1-2°C (2-3°F)?

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Go to Step 7

Go to Step 3

3

Did the customer 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 4

Go to Step 5

4

Increase engine speed to 2,000 RPM.

During extended operation of the A/C system, does the low side pressure decrease, possibly accompanied by heavy frost on the liquid line between the expansion device and the evaporator?

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Go to Air Conditioning (A/C) Diagnostics - Pressure Zone D

Go to Step 5

5

Refer to the pressures recorded during the A/C system performance test.

Inspect for the following conditions:

Caution: Refer to Moving Parts and Hot Surfaces Caution in the Preface section.

    • The high side pressure is slightly greater than the specified pressure ranges but still within Zone A on the A/C Pressure-Zone Classification Chart in the A/C System Performance Test. Refer to Air Conditioning (A/C) System Performance Test .
    • The discharge line is hot.
    • The suction line is cool.

Do the listed conditions exist?

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Go to Step 7

Go to Step 6

6

Refer to the pressures recorded during the A/C system performance test.

Inspect for the following conditions:

    • The low side pressure is slightly lower than the specified pressure ranges but still within Zone A on the A/C Pressure-Zone Classification Chart in the A/C System Performance Test. Refer to DTC B0238, B0239, B0248, B0249, B0251, B0268, B0269, B0408, B0409, B0414, B0418, B0419, B0424, B0428, B0429, B0434, B3531, B3532, B3747, B3749 or B3782 .
    • The discharge line is warm-to-hot.
    • The suction line is cool-to-warm.

Do the listed conditions exist?

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Go to Step 8

Go to Too Hot in Vehicle

7

The A/C system may be undercharged.

  1. Leak test the A/C system. Refer to Leak Testing .
  2. Recharge the A/C system to specifications. Refer to Refrigerant Recovery and Recharging .

Is the repair complete?

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Go to Step 14

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8

The A/C system may be contaminated.

View the J 43600 ACR 2000 Air Conditioning Service Center information screen for detection of foreign gases in the A/C system.

Do foreign gases exist?

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Go to Step 9

Go to Step 10

9
  1. Evacuate the A/C system to a scavenging tank. Refer to Refrigerant Recovery and Recharging .
  2. Recharge the A/C system to specifications.

Is the repair complete?

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Go to Step 14

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10

The A/C system may contain too much moisture or air.

  1. Evacuate and recharge the A/C system to specifications. Refer to Refrigerant Recovery and Recharging .
  2. Operate the A/C system and inspect the panel outlet air temperatures. Refer to Air Conditioning (A/C) System Performance Test .

Are the panel outlet temperatures within the specified ranges of the A/C Performance Test Table?

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Go to Step 15

Go to Step 11

11

The A/C system may contain too much refrigerant oil.

    Important: Operate the A/C system on low in order to enhance oil flow to the high side of the system.

  1. Operate the A/C system with the engine at idle speed and the blower speed on low for approximately 15 minutes.
  2. Recover the refrigerant from the A/C system. Refer to Refrigerant Recovery and Recharging .
  3. Remove the receiver dehydrator. Refer to Receiver Dehydrator Replacement .
  4. Drain and measure the refrigerant oil from the receiver dehydrator.

Is the amount of refrigerant oil drained from the receiver greater than the specified value?

148 ml (5 oz)

Go to Step 12

Go to Step 13

12
  1. Reinstall the receiver dehydrator. Refer to Receiver Dehydrator Replacement .
  2. Flush the A/C system. Refer to Flushing .
  3. Recharge the A/C system. Refer to Refrigerant Recovery and Recharging .

Are the repairs complete?

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Go to Step 14

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13
  1. Add the specified amount of refrigerant oil to the receiver dehydrator. Refer to Refrigerant System Capacities .
  2. Install the receiver dehydrator. Refer to Receiver Dehydrator Replacement .
  3. Recharge the A/C system. Refer to Refrigerant Recovery and Recharging .

Are the repairs complete?

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Go to Step 14

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14
  1. Record the low and high side pressures and the instrument panel (I/P) outlet air temperature.
  2. Compare the panel outlet temperatures to those listed in the A/C System Performance Chart. Refer to Air Conditioning (A/C) System Performance Test .

Are the high and low side pressures and I/P outlet temperatures within specifications?

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Go to Step 15

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

15

Operate the system in order to verify the repair.

Did you find and correct the condition?

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System OK

Go to Symptoms - HVAC Systems - Manual