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

Step

Action

Yes

No

DEFINITION: The low and the high side pressures are both higher than normal.

    • Restricted Condenser Air Flow
    • Cooling Fan Malfunction
    • Expansion Devise Malfunction

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
  1. Start the engine.
  2. Turn ON the A/C.
  3. Inspect for proper cooling fan operation. Refer to Cooling System Description and Operation .

Are the cooling fans ON and operating properly?

Go to Step 3

Go to Step 5

3

Visually inspect for the following conditions:

    • Damaged condenser cooling fins
    • Missing or misaligned air baffles
    • Restricted air flow

Do any of these conditions exist?

Go to Step 4

Go to Step 6

4

Repair the air flow restriction.

Is the action complete?

Go to Step 9

--

5

Repair the fault to the cooling fan operation fault. Refer to Cooling Fan Inoperative .

Is the action complete?

Go to Step 9

--

6

Caution: Avoid contact with moving parts and hot surfaces while working around a running engine in order to prevent physical injury.

Feel the liquid line on both sides of the expansion device.

Are the temperatures on both side of the expansion device similar?

Go to Step 7

Go to Step 8

7

Replace the damaged or faulty expansion devise. Refer to Thermal Expansion Valve Replacement .

Is the action complete?

Go to Step 9

--

8
  1. Air is in the refrigerant system, or the system is overcharged. Refer to the view screen on the J 43600 ACR 2000 Air Conditioning Service Center for foreign gas content in the refrigerant.
  2. Recover and recharge the A/C system. Refer to Refrigerant Recovery and Recharging .

Is the action complete?

Go to Step 9

--

9
  1. Record the low and high side pressures and the instrument panel outlet air temperature after you have performed the repairs.
  2. Compare the pressures and 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 listed in the A/C Performance Chart?

Go to Step 10

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

10

Operate the system in order to verify the repair.

Did you find and correct the condition?

System OK

Go to Symptoms - HVAC Systems - Automatic or Symptoms - HVAC Systems - Manual