Were you sent here from the Cooling Insufficient, A/C System -- Pressure Zone A diagnostic table?

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Go to Step 3

Go to Step 2

Were you sent here from the Cooling Insufficient, A/C System diagnostic table?

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Go to Step 3

Go to Cooling Insufficient - Air Conditioning (A/C) System

1. The engine still idling in PARK.
2. The HVAC control head still set to the following positions:

•	A/C button to ON

•	Temperature control to full cold

•	Mode control knob to UPPER (I/P outlets)

•	Blower switch to 5 (high)

3. Close the vehicle windows and doors.
4. The vehicle hood fully raised.
5. Both engine cooling fans operating.
6. Elevate and maintain the engine speed to 3000 RPM.
7. Cycle the A/C from ON to OFF to ON -- by depressing the A/C button on the HVAC control head -- every 20 seconds for 3 minutes.
8. Record the low and high side pressure readings.

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

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Go to Step 4

Go to Step 11

Is the pressure rise slow on both the low and high side gages?

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Go to Step 10

Go to Step 5

1. Turn the engine OFF.
2. Ensure that the compressor clutch is disengaged.
3. Attempt to rotate the compressor clutch driver (NOT the pulley) by hand.

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

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Go to Step 10

Go to Step 6

1. Start the engine and allow the engine to idle.
2. Turn the A/C ON by depressing the A/C button on the HVAC control head.
3. Observe the low side pressure readings.
4. Elevate the engine speed to between 3000-3800 RPM.

Is there a rapid rise in the low side pressure between 3000-3800 engine RPM?

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Go to Step 7

Go to Step 10

1. Elevate and maintain the engine speed at 2000 RPM.
2. The HVAC control head still set to the following positions:

•	A/C button to ON

•	Temperature control to full cold

•	Mode control knob to UPPER (I/P outlets)

3. Set the blower switch to 1 (low).
4. The vehicle windows and doors still closed.
5. The vehicle hood still fully raised.
6. Both engine cooling fans operating.
7. Record the low side pressure reading.

Is the low side pressure reading within the specified values?

172-241 kPa (25-35 psi)

Go to Step 8

Go to Step 9

1. The engine still idling in PARK.
2. The HVAC control head set to the following positions:

•	A/C button to ON

•	Temperature control to full cold

•	Mode control knob to UPPER (I/P outlets)

•	Blower switch to 5 (high)

3. Elevate and maintain the engine speed at 2000 RPM.
4. Allow the low and high side pressure readings to stabilize, if necessary.

(Stabilization usually requires 2-3 minutes.)

5. Record the low and high pressure readings.
6. Compare the low and high side pressures to the A/C System Pressure -- Zone Classification Chart above.

Refer to

A/C System Pressure -- Zone Classification



.

Do both the low and high side pressures fall within Zone B on the chart (low side pressure still high and high side pressure still low)?

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Go to Step 10

Go to Step 11

1. Recover the refrigerant.
2. Replace the control valve.

Refer to Compressor Pressure Relief Valve Replacement .

Is the repair complete?

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Go to Step 12

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1. Recover the refrigerant.
2. Replace the A/C compressor.

Refer to Air Conditioning Compressor Replacement .

Is the repair complete?

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Go to Step 12

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1. Start the engine and allow the engine to idle.
2. An accurate thermometer still installed to the I/P center air outlet.
3. Set the HVAC control head to the following positions:

•	A/C button to ON

•	Temperature control to full cold

•	Mode control knob to UPPER (I/P outlets)

•	Blower switch to 5 (high)

4. Elevate and maintain the engine speed at 2000 RPM.
5. Allow the low and high side pressure readings to stabilize, if necessary.

(Stabilization usually requires 2-3 minutes.)

6. Record the low and high pressure readings and the delivered air output temperature.
7. Compare the low and high side pressures and the output temperatures to those listed in the A/C System Performance Chart.

Refer to System Performance Test .

Are both the low and high side pressures as well as the output temperatures within specifications?

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System OK

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1. Evacuate and charge the refrigerant system.
2. Leak test the refrigerant system.

Refer to Leak Testing .

Are the operations completed?

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Go to Step 13

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1. Start the engine and allow the engine to idle.
2. An accurate thermometer still installed to the I/P center air outlet.
3. Set the HVAC control head to the following positions:

•	A/C button to ON

•	Temperature control to full cold

•	Mode control knob to UPPER (I/P outlets)

•	Blower switch to 5 (high)

4. Elevate and maintain the engine speed at 2000 RPM.
5. Allow the low and high side pressure readings to stabilize, if necessary.

(Stabilization usually requires 2-3 minutes.)

6. Record the low and high pressure readings and the delivered air output temperature.
7. Compare the low and high side pressures and the output temperatures to those listed in the A/C System Performance Chart.

Refer to System Performance Test .

Are both the low and high side pressures as well as the output temperatures within specifications?

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Go to HVAC System Check

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