VDOT Air Conditioning (A/C) System Diagnosis. Pontiac Grand Am 2000

For 1990-2009 cars only

Makes 🢒 Pontiac 🢒 2000 🢒 Grand Am 🢒 HVAC 🢒 Heating, Ventilation and Air Conditioning 🢒 VDOT Air Conditioning (A/C) System Diagnosis

VDOT Air Conditioning (A/C) System Diagnosis Preliminary Checks

Use the following diagnostic tables in order to diagnose insufficient cooling conditions with the following systems:

•	The V5 compressor

•	The VDOT refrigerant system

Use these procedures in conjunction with other appropriate service manual information.

The V5 compressor is a variable displacement compressor. The V5 compressor matches the air conditioning demand by changing the stroke instead of cycling the clutch. A control valve is located in the rear head of the compressor. The control valve senses compressor low side pressure and causes the compressor to change the stroke. Because the V5 compressor always runs and the system does not cycle, these diagnostic procedures differ from procedures used for fixed displacement systems. Use these procedures in order to avoid needlessly replacing the A/C components.

Preliminary Checks

Repair the following components as needed. If the air discharge air temperature with the A/C ON is normal after repairing the following components, the system is operating properly:

•	The A/C fuse

•	The A/C blower operation

•	The temperature door

Move the temperature door rapidly from the COLD position to the HOT position. Listen for the temperature door hitting at each end. Adjust the door as needed. (Cable-operated temperature door only)

•	The clutch coil

•	The rear head switch connections

•	The drive belt

Adjust the belt as needed. Replace the belt if the belt is damaged or missing. Refer to Drive Belt Replacement in Engine Mechanical 2.4L or Drive Belt Replacement in Engine Mechanical 3.4L.

•	The engine cooling fan operation

•	The condenser

Inspect the condenser for restricted air flow.

Consult Dealer Technical Bulletins and the Service Guild for updates on the A/C system.

Refer to VDOT Air Conditioning (A/C) System Diagnosis .

VDOT Air Conditioning (A/C) System Diagnosis Checking Refrigerant Charge

Checking Refrigerant Charge

Step	Action	Value(s)	Yes	No
1	Ensure that the pressure gauges are properly calibrated. Ensure that the ambient air is at least 16°C (60°F). Warm the engine to operating temperature. Turn the ignition key to the OFF position. Connect the high side and the low side pressure gauges. Ensure that the pressures are approximately equal. Are both pressures below the specified value?	345 kPa (50 psi)	Go to Step 2	Go to Step 5
2	Are both pressures within the specified range?	69-345 kPa (10-50 psi)	Go to Step 3	Go to Step 4
3	Inspect the system for leaks. Refer to Leak Testing . Evacuate and charge the system. Refer to Refrigerant Recovery and Recharging . Are both pressures above the specified value?	345 kPa (50 psi)	System OK	--
4	Add 0.45 kg (1.0 lb) of refrigerant to the system. Inspect the system for leaks. Refer to Leak Testing . Evacuate and charge the system. Refer to Refrigerant Recovery and Recharging . Are both pressures above the specified value?	345 kPa (50 psi)	System OK	--
5	Are both pressures above the specified value?	345 kPa (50 psi)	System OK	--

VDOT Air Conditioning (A/C) System Diagnosis Checking Compressor Clutch Engagement

Step

Action

Value(s)

Yes

Run the engine at idle.
Set the A/C control to NORM.
Set the blower control to the HIGH position.
Set the temperature control to the FULL COLD position.

Does the clutch engage?

Go to Step 2

Go to Step 6

Inspect the system for the following conditions:

•	A loud knocking noise from the compressor (cycle the compressor ON and OFF in order to verify the source of the noise)

•	A slipping belt condition

Does a slipping belt condition exist?

Go to Step 3

Go to Step 4

Tighten the belt as needed.

Is the repair complete?

Go to Step 4

Does a compressor noise exist?

Go to Step 5

System OK

Replace the compressor. Refer to Air Conditioning Compressor Replacement .

Is the repair complete?

System OK

Turn the ignition switch to the OFF position.
Disconnect the clutch wires at the compressor.
Connect a jumper wire from ground to one of the compressor clutch terminals.
Connect a fused-jumper wire from the positive battery post to the other compressor clutch terminal.
Run the engine at idle.

Does the clutch engage?

Go to Step 7

Go to Step 9

Repair the electrical circuit to the compressor clutch.

Is the repair complete?

Go to Step 8

Run the engine at idle.
Set the A/C control to NORM.
Set the blower control to the HIGH position.
Set the temperature control to the FULL COLD position.

Does the clutch engage?

System OK

Replace the clutch coil.

Is the repair complete?

System OK

VDOT Air Conditioning (A/C) System Diagnosis Checking System Performance

Step

Action

Value(s)

Yes

Important: This test is designed for the following garage conditions:

•	21-32°C (70-90°F)

•	No sun load

Normal discharge temperature is typically at least 7°C (20°F) cooler than the ambient temperature. Follow the steps in this test exactly. The test is designed in order to create enough cooling load in order to cause the V5 to operate at full stroke. This condition is absolutely necessary in order to obtain accurate test results.

Close all of the vehicle windows and doors.
Set the A/C control to NORM.
Set the blower control to the HIGH position.
Set the temperature control to the FULL COLD position.
Run the engine at idle for 5 minutes.
Feel the liquid line on both sides of the orifice (expansion) tube.

Are both sides of the line the same temperature?

Go to Step 2

Go to Step 5

Recover the refrigerant. Refer to Refrigerant Recovery and Recharging .

Is the orifice (expansion) tube missing?

Go to Step 3

Go to Step 4

Install the orifice (expansion) tube. Refer to Leak Testing .

Is the repair complete?

Go to Step 4

Evacuate and charge the system. Refer to Refrigerant Recovery and Recharging .
Leak test the system. Refer to Leak Testing .
Observe the discharge air temperature.

Is the discharge air temperature at least 7°C (20°F) cooler than the ambient temperature?

System OK

Go to Step 1

Operate the A/C system for more than 5 minutes.
Record the low side and the high side pressures.

On engines with cycling cooling fans, record the pressures with the engine cooling fan ON.

Determine the intersection of the low side and the high side pressures on the above chart.

Do the low side and the high side pressures intersect in the striped area of the above chart?

Go to Step 6

Go to Step 15

Are the compressor high side and the low side pressures within 207 kPa (30 psi) of each other?

Go to Step 7

Go to Step 10

Run at 3,000 RPM.
Set the blower control to the HIGH position.
Set the temperature control to the FULL COLD position.
Close all of the vehicle windows and doors.
Cycle the mode lever from VENT to A/C every 20 seconds for 3 minutes.

Are the compressor high side and the low side pressures within 207 kPa (30 psi) of each other?

Go to Step 8

Go to Step 1

Turn the ignition switch to the OFF position.
Disengage the compressor clutch.

Does the compressor clutch driver (not the pulley) turn freely by hand?

Go to Step 9

Go to

VDOT Air Conditioning (A/C) System Diagnosis

Replace the compressor. Refer to Air Conditioning Compressor Replacement .

Is the repair complete?

Go to Step 1

Is the low side pressure within the specified range?

172-241 kPa

(25-35 psi)

Go to Step 11

Go to

VDOT Air Conditioning (A/C) System Diagnosis

If the refrigerant is under-charged, add 0.40 kg (14 oz) of refrigerant to the system.

Does the cooling performance improve?

Go to Step 12

Go to Step 13

Leak test the system. Refer to Leak Testing . Repair any leaks as needed.

Are all necessary repairs complete?

Go to Step 20

Recover the refrigerant. Refer to Refrigerant Recovery and Recharging .
Inspect the orifice (expansion) tube.

Is the tube plugged?

Go to Step 14

Go to Step 20

Remove the orifice (expansion) tube. Refer to Expansion (Orifice) Tube Replacement
Clear the lines.
Replace the orifice (expansion) tube. Refer to Expansion (Orifice) Tube Replacement .

If only light debris is present in the tube, clean the tube using compressed air.

Are all necessary repairs complete?

Go to Step 20

Do the low side and high side pressures intersect in the grey area of the above chart?

Go to Step 17

Go to Step 16

The low side and high side pressures intersect in the normal (white) area of the above chart.

Does insufficient cooling exist?

Go to Air Delivery Improper

System OK

Run the engine at idle.
Set the A/C control to NORM.
Set the blower control to the HIGH position.
Set the temperature control to the FULL COLD position.
Close all of the vehicle windows and doors.
Feel the liquid line between the condenser and the orifice (expansion) tube.

Is the line cold?

Go to Step 18

Go to Step 19

A restriction exists in the high side. Perform the following steps:

Recover the refrigerant. Refer to Refrigerant Recovery and Recharging .
Remove the restriction in the high side.

Is the line clear?

Go to Step 20

One of the following conditions exists:

•	The refrigerant is overcharged.

•	Air is in the system.

Recover the refrigerant. Refer to Refrigerant Recovery and Recharging .

Has the refrigerant been recovered?

Go to Step 20

Evacuate and charge the system. Refer to Refrigerant Recovery and Recharging .
Leak test the system. Refer to Leak Testing . Repair any leaks as needed.

Are all of the procedures complete?

Go to Step 1

VDOT Air Conditioning (A/C) System Diagnosis Control Valve Diagnosis

Step	Action	Value(s)	Yes	No
Important: Follow the steps in this test procedure exactly. This test is designed in order to create a low cooling load. This condition causes the V5 compressor to operate at less than full stroke. This condition is absolutely necessary in order to obtain accurate test results.
1	Run the engine at 2,000 RPM for 5 minutes. Set the A/C control to MAX. Set the blower control to the LOW position. Set the temperature control to the FULL COLD position. Close all of the vehicle windows and doors. Open the hood. Is the low side pressure within the specified range?	172-241 kPa (25-35 psi)	Go to VDOT Air Conditioning (A/C) System Diagnosis	Go to Step 2
2	Recover the refrigerant. Refer to Refrigerant Recovery and Recharging . Replace the control valve. Refer to Compressor Control Valve Assembly Install . Evacuate and charge the system. Refer to Refrigerant Recovery and Recharging Test the system. Refer to Leak Testing . Are all of the procedures complete?	--	Go to VDOT Air Conditioning (A/C) System Diagnosis	--

Step

Action

Value(s)

Yes

Important: Follow the steps in this test procedure exactly. This test is designed in order to create a low cooling load. This condition causes the V5 compressor to operate at less than full stroke. This condition is absolutely necessary in order to obtain accurate test results.

Run the engine at 2,000 RPM for 5 minutes.
Set the A/C control to MAX.
Set the blower control to the LOW position.
Set the temperature control to the FULL COLD position.
Close all of the vehicle windows and doors.
Open the hood.

Is the low side pressure within the specified range?

172-241 kPa

(25-35 psi)

Go to VDOT Air Conditioning (A/C) System Diagnosis

Go to Step 2

Recover the refrigerant. Refer to Refrigerant Recovery and Recharging .
Replace the control valve. Refer to Compressor Control Valve Assembly Install .
Evacuate and charge the system. Refer to Refrigerant Recovery and Recharging
Test the system. Refer to Leak Testing .

Are all of the procedures complete?

Go to VDOT Air Conditioning (A/C) System Diagnosis