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Air Conditioning (A/C) Diagnostics - Pressure Zone D

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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.
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 (Short Wheel Base)  or Air Conditioning (A/C) System Performance Test (Long Wheel Base - 1500 Series)  or Air Conditioning (A/C) System Performance Test (Long Wheel Base - 2500 Series) 
2
CAUTION: Refer to Moving Parts and Hot Surfaces Caution .
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 inlet tube between the expansion device and the evaporator core
  • The evaporator outlet tube between the evaporator core and the compressor
  • The accumulator
  • 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 inlet tube between the expansion device and the evaporator core
  • The evaporator outlet tube between the evaporator core and the accumulator
  • The accumulator
  • 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 repair 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 repair complete?		 Go to Step 21  -
11 The expansion device is restricted.
Replace the expansion device. Refer to Expansion (Orifice) Tube Replacement (W/O C69)  or Expansion (Orifice) Tube Replacement (W/C69) .
Are metal flakes present?		 Go to Step 12  Go to Step 13 
12
  1. Remove the suction line from the vehicle. Refer to Suction Hose Replacement (W/O C69)  or Suction Hose Replacement (W/C69) .
  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 accumulator. Refer to Accumulator Replacement .

Are the repairs complete?		 Go to Step 21  -
14
  1. Recover the refrigerant. Refer to Refrigerant Recovery and Recharging .
  2. Disconnect the suction and the discharge lines from the compressor. Refer to Suction Hose Replacement (W/O C69)  or Suction Hose Replacement (W/C69)  and Discharge Hose 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 Expansion (Orifice) Tube Replacement (W/O C69)  or Expansion (Orifice) Tube Replacement (W/C69) .
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 suction line from the vehicle. Refer to Suction Hose Replacement (W/O C69)  or Suction Hose Replacement (W/C69) .
  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 Expansion (Orifice) Tube Replacement (W/O C69)  or Expansion (Orifice) Tube Replacement (W/C69) .
  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 compressor hose assembly, perform the following procedure:
Replace the accumulator. Refer to Accumulator Replacement .
Is the repair complete?		 Go to Step 19  -
19 Install the suction and the discharge lines. Refer to Suction Hose Replacement (W/O C69)  or Suction Hose Replacement (W/C69)  and Discharge Hose Replacement .
Are the repairs complete?		 Go to Step 21  -
20
  1. Install the suction and the discharge lines. Refer to Suction Hose Replacement (W/O C69)  or Suction Hose Replacement (W/C69)  and Discharge Hose Replacement .
  2. Recharge the A/C system. Refer to Refrigerant Recovery and Recharging .
Are the repairs complete?		 Go to Step 21  -
21
  1. Record the low and the high side pressures and the panel outlet air temperature after you perform the repairs.
  2. Compare the pressures and the panel outlet temperature to those listed in the A/C Performance Chart. Refer to Air Conditioning (A/C) System Performance Test (Short Wheel Base)  or Air Conditioning (A/C) System Performance Test (Long Wheel Base - 1500 Series)  or Air Conditioning (A/C) System Performance Test (Long Wheel Base - 2500 Series) .
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 (Short Wheel Base)  or Air Conditioning (A/C) System Performance Test (Long Wheel Base - 1500 Series)  or Air Conditioning (A/C) System Performance Test (Long Wheel Base - 2500 Series) 
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
Symptoms - HVAC Systems - Automatic
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