GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Chevrolet 🢒 2007 🢒 Corvette 🢒 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 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:

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

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 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 Step 6

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 11

--

6

The A/C compressor is malfunctioning.

Remove the refrigerant filter and inspect for contamination. Refer to Air Conditioning (AC) Refrigerant Filter Replacement .

Did you find metal flakes on the refrigerant filter?

Go to Step 8

Go to Step 7

7

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

Is a brown, powdery residue present?

Go to Step 9

Go to Step 10

8
  1. Replace the refrigerant filter. Refer to Air Conditioning (AC) Refrigerant Filter Replacement .
  2. Evacuate and recharge the A/C system. Refer to Refrigerant Recovery and Recharging .

Is the repair complete?

Go to Step 11

--

9
  1. Flush the A/C system. Refer to Flushing .
  2. Replace the thermal expansion valve. Refer to Thermal Expansion Valve Replacement .
  3. Replace the A/C compressor. Refer to Air Conditioning Compressor Replacement .
  4. Replace the condenser. Refer to Condenser Replacement .
  5. Evacuate and recharge the A/C system. Refer to Refrigerant Recovery and Recharging .

Is the repair complete?

Go to Step 11

--

10
  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 11

--

11

Operate the system in order to verify the repair.

Did you find and correct the condition?

System OK

Go to Symptoms - HVAC Systems - Automatic