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

Step

Action

Value

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 at the front of dash.

Is the liquid line cold at the front of dash?

--

Go to Step 3

Go to Step 8

3

Feel along the surface of the liquid line between the condenser and the front of dash.

Did you detect an abrupt drop in temperature along the surface?

--

Go to Step 5

Go to Step 4

4

Feel along the surfaces of the following low side components:

    • The evaporator outlet tube between the front of dash and the compressor suction hose
    • The compressor suction hose to the compressor.

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

--

Go to Step 5

Go to Step 6

5
  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.
  3. Recharge the A/C system. Refer to Refrigerant Recovery and Recharging .

Is the repair complete?

--

Go to Step 13

--

6

The system may be low charged.

  1. Recover the refrigerant. Refer to Refrigerant Recovery and Recharging .
  2. Record the weight of the recovered refrigerant.

Is the weight of the recovered refrigerant charge less than the specified value?

Standard AC 0.625 kg (1.38 lbs)

Go to Step 7

Go to Step 10

7

The expansion device may be restricted or failed.

  1. Remove the expansion device. Refer to Thermal Expansion Valve Replacement .
  2. Check the expansion device for a large amount residue at the inlet.

Did you notice a residue at the inlet to the expansion device?

--

Go to Step 8

Go to Step 11

8

The desiccant bag in the receiver portion of the condenser may have failed.

  1. Remove the desiccant bag from the condenser. Refer to Air Conditioning Refrigerant Desiccant Replacement .
  2. Check to see if the bag was broken.

Was the bag broken or leaking?

--

Go to Step 9

Go to Step 12

9
  1. Flush the A/C system. Refer to Flushing .
  2. Replace the condenser. Refer to Condenser Replacement .
  3. Recharge the A/C system. Refer to Refrigerant Recovery and Recharging .

Are the repairs complete?

--

Go to Step 13

--

10
  1. Leak test the system. Refer to Leak Testing .
  2. Repair any leaks found.
  3. Recharge the A/C system. Refer to Refrigerant Recovery and Recharging .

Are the repairs complete?

--

Go to Step 13

--

11
  1. Replace the expansion device.
  2. Recharge the A/C system. Refer to Refrigerant Recovery and Recharging .

Are the repairs complete?

--

Go to Step 13

--

12
  1. Replace the desiccant bag with a new unit.
  2. Replace the expansion device.
  3. Recharge the A/C system. Refer to Refrigerant Recovery and Recharging .

Are the repairs complete?

--

Go to Step 13

--

13
  1. Record the low and the high side pressures and the panel outlet air temperature.
  2. Compare the pressures and the panel outlet temperature to those listed in the A/C Performance Table. Refer to Air Conditioning (A/C) System Performance Test .

Are the readings within the specified ranges as shown on the A/C performance Table?

--

Go to Step 14

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

14

Operate the system in order to verify the repair.

Did you find and correct the condition?

--

System OK

Go to Symptoms - HVAC Systems - Automatic