GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 GMC_Truck 🢒 2009 🢒 Yukon - 2WD 🢒 HVAC 🢒 Heating, Ventilation, and Air Conditioning 🢒 Air Conditioning (A/C) Diagnostics - Pressure Zone B

Step

Action

Yes

No

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

    • Malfunctioning A/C Compressor
    • Refrigerant Under Charge

1

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

Go to Step 2

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

2

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

Go to Step 5

Go to Step 3

3

Refer to the pressures recorded during the A/C System Performance Test.

Inspect for the following conditions:

Warning: Refer to Moving Parts and Hot Surfaces Warning 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

Refer to the pressures recorded during the A/C System Performance Test.

Inspect for the following conditions:

Warning: Refer to Moving Parts and Hot Surfaces Warning 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 procedure complete?

Go to Step 6

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6
  1. Record the low and the high side pressures as well as the instrument panel (I/P) air outlet temperature after you perform the repairs.
  2. Compare the pressures and the panel outlet 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 expansion device and inspect for contamination. Refer to Expansion (Orifice) Tube Replacement.

Did you find metal flakes on the expansion device?

Go to Step 9

Go to Step 8

8

Inspect the expansion device 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 suction and the discharge lines from the compressor. Refer to Suction Hose Replacement and to Discharge Hose 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. Install an A/C refrigerant filter. Refer to Air Conditioning (AC) Refrigerant Filter Replacement.
  3. Replace the orifice tube. Refer to Expansion (Orifice) Tube Replacement.
  4. Evacuate and recharge the A/C system. Refer to Refrigerant Recovery and Recharging.

Is the repair complete?

Go to Step 13

--

11
  1. Flush the A/C system. Refer to Flushing.
  2. Replace the orifice tube. Refer to Expansion (Orifice) Tube Replacement.
  3. Replace the A/C compressor. Refer to Air Conditioning Compressor Replacement.
  4. Replace the accumulator. Refer to Air Conditioning Accumulator Replacement.
  5. Evacuate and recharge the A/C system. Refer to Refrigerant Recovery and Recharging.

Is the repair complete?

Go to Step 13

--

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 repair complete?

Go to Step 13

--

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