GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Pontiac 🢒 2007 🢒 Grand Prix 🢒 HVAC 🢒 Heating, Ventilation, and Air Conditioning 🢒 Air Conditioning (A/C) Diagnostics - Pressure Zone D

Step

Action

Yes

No

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

    •  A restriction in the A/C system
    • Debris in the system

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

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

Feel the liquid line before the expansion device.

Is the liquid line cold before the expansion device?

Go to Step 3

Go to Step 8

3

Feel along the surfaces of the following high side components:

    • The compressor discharge hose
    • The condenser
    • The liquid line between the condenser and the expansion device

Did you detect an abrupt drop in temperature along the surfaces of any of the listed components?

Go to Step 7

Go to Step 4

4
  1. Feel the liquid line at the expansion device location for extreme cold, possibly accompanied by heavy frost.
  2. Feel along the liquid line beyond the expansion device location for warm temperature.

Is the liquid line extremely cold at the expansion device location and warm beyond the expansion device location?

Go to Step 11

Go to Step 5

5

Feel along the surfaces of the following low side components:

    • The evaporator thermal expansion valve tube between the expansion device and the compressor suction hose
    • The compressor suction hose

Did you feel an abrupt temperature change along the surfaces of any of the listed components?

Go to Step 7

Go to Step 6

6

Feel along the surfaces of the low and the high side components.

    • The evaporator thermal expansion valve tube between the expansion device and the compressor suction hose
    • The compressor suction hose
    • The compressor discharge hose
    • The condenser
    • The evaporator inlet tube between the condenser and the expansion device

Are the temperatures of these components only mildly warm?

Go to Step 14

Go to Step 8

7
  1. Recover the refrigerant. Refer to Refrigerant Recovery and Recharging .
  2. Remove the restriction from the component, or replace the component which produced an abrupt temperature drop.

Is the action complete?

Go to Step 9

--

8
  1. Recover the refrigerant and evacuate the system. Refer to Refrigerant Recovery and Recharging .
  2. Record the weight of the recovered refrigerant.
  3. Compare the weight of the recovered refrigerant with the system capacity. Refer to Refrigerant System Capacities .

Is the weight of the recovered refrigerant charge greater than 75 percent of the total system capacity?

Go to Step 9

Go to Step 10

9

Recharge the A/C System. Refer to Refrigerant Recovery and Recharging .

Is the cooling performance improved?

Go to Step 21

Go to Step 10

10
  1. Leak test the system. Refer to Leak Testing .
  2. Repair any leaks.

Is the action complete?

Go to Step 21

--

11

The expansion device is restricted.

  1. Replace the expansion device. Refer to Thermal Expansion Valve Replacement .
  2. If the expansion device was restricted, note the type of debris present.

Are metal flakes present?

Go to Step 12

Go to Step 13

12
  1. Remove the compressor hose assembly from the vehicle. Refer to Compressor Hose Assembly Replacement .
  2. Inspect the hose for debris by blowing shop air through one end of the hose while covering the other end with a shop towel.
  3. Observe the amount of debris collected in the shop towel.

Did a large amount of debris collect in the shop towel?

Go to Step 18

Go to Step 20

13

If the expansion device was restricted with a brown or black residue, perform the following procedure:

  1. Flush the A/C System. Refer to Flushing .
  2. Replace the A/C refrigerant filter. Refer to Air Conditioning (AC) Refrigerant Filter Replacement .
  3. Replace the condenser. Refer to Condenser Replacement .

Are the actions complete?

Go to Step 21

--

14
  1. Recover the refrigerant. Refer to Refrigerant Recovery and Recharging .
  2. Disconnect the compressor hose from the compressor. Refer to Compressor Hose Assembly Replacement .
  3. Inspect for the presence of debris in the compressor suction port.

Is debris present in the compressor suction port?

Go to Step 15

Go to Step 19

15
  1. Remove the debris from the suction port.
  2. Inspect the expansion device for damage or debris. Refer to Thermal Expansion Valve Replacement .

Did you find evidence of damage or debris?

Go to Step 17

Go to Step 16

16

If the expansion device does not show any signs of damage or debris, perform the following procedure:

  1. Remove the compressor hose assembly from the vehicle. Refer to Compressor Hose Assembly Replacement .
  2. Inspect the hose for debris by blowing shop air through one end of the hose while covering the other end with a shop towel.
  3. Observe the amount of debris collected in the shop towel.

Did a large amount of debris collect in the shop towel?

Go to Step 18

Go to Step 19

17
  1. Replace the expansion device. Refer to Thermal Expansion Valve Replacement .
  2. If the expansion device was restricted, observe the type of debris present.

Are metal flakes present?

Go to Step 12

Go to Step 13

18

If a large amount of debris was collected in the shop towel from the suction hose, perform the following procedure:

    • Install an A/C compressor suction screen or replace the screen if one was previously installed. Refer to Suction Screen Replacement .
    • Replace the A/C condenser. Refer to Condenser Replacement .
    • Replace the A/C refrigerant filter. Refer to Air Conditioning (AC) Refrigerant Filter Replacement .

Is the action complete?

Go to Step 19

--

19

Install the compressor hose assembly. Refer to Compressor Hose Assembly Replacement .

Is the action complete?

Go to Step 21

--

20
  1. Install the compressor hose assembly. Refer to Compressor Hose Assembly Replacement .
  2. Recharge the A/C system. Refer to Refrigerant Recovery and Recharging .

Are the actions complete?

Go to Step 21

--

21
  1. Record the low and the high side pressures and the instrument panel outlet air temperature after you perform the repairs.
  2. Compare the pressures and the instrument panel outlet air 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 as shown on the A/C Performance Chart?

Go to Step 22

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

22

Operate the system in order to verify the repair.

Did you find and correct the condition?

System OK

Go to Symptoms - HVAC Systems - Manual

or

Go to Symptoms - HVAC Systems - Automatic